Following Hy's suggestion starting new topic about trouble I am having with new internal guider.  First the original post:

I don’t know if it is related to new guider but I am seeing occasional exposure timeouts on my guide camera (ZWO ASI290mm mini).  This freezes the whole process for a minute or so.  I have not previously seen this.  Running kstars/ekos 3.5.5 on Ubuntu 20.04.  The exposure timeout correlated with dark subtraction ceasing to work properly.  It was working fine, camera timed out, after camera and guiding returned the dark subtraction was resulting in loss of stars and I had to disable it.  It’s unfortunate as dark subtraction improved guiding to 0.65 arc second rms from 0.85, at least that was the effect tonight.

When the camera isn’t frozen the new internal guider is working fine for me including gpg, dithering, and multi-star.

Here is the log from a freeze that coincided with a dither (this was probably random as it has also frozen in the middle of a sub):

2021-09-20T21:03:48.652 MDT INFO ][   org.kde.kstars.ekos.capture] - Dithering...
[2021-09-20T21:03:48.652 MDT INFO ][   org.kde.kstars.ekos.capture] - "Dithering..."
[2021-09-20T21:03:48.654 MDT INFO ][     org.kde.kstars.ekos.guide] - "Dithering in progress."
[2021-09-20T21:04:22.095 MDT INFO ][     org.kde.kstars.ekos.guide] - "Exposure timeout. Restarting exposure..."
[2021-09-20T21:04:53.095 MDT INFO ][           org.kde.kstars.ekos] - "ZWO CCD ASI290MM Mini is offline."
[2021-09-20T21:04:54.139 MDT INFO ][           org.kde.kstars.ekos] - Ekos received a new device:  "ZWO CCD ASI290MM Mini"
[2021-09-20T21:04:54.341 MDT INFO ][           org.kde.kstars.indi] - ZWO CCD ASI290MM Mini :  "[INFO] Setting intital bandwidth to AUTO on connection. "
[2021-09-20T21:04:54.351 MDT INFO ][           org.kde.kstars.indi] - ZWO CCD ASI290MM Mini :  "[INFO] CCD is online. Retrieving basic data. "
[2021-09-20T21:04:54.352 MDT INFO ][           org.kde.kstars.ekos] - All INDI devices are now connected.
[2021-09-20T21:04:54.629 MDT INFO ][           org.kde.kstars.ekos] - "ZWO CCD ASI290MM Mini is online."
[2021-09-20T21:04:54.639 MDT INFO ][           org.kde.kstars.ekos] - "Guider port from ZWO CCD ASI290MM Mini is ready."
[2021-09-20T21:04:54.650 MDT INFO ][           org.kde.kstars.indi] - ZWO CCD ASI290MM Mini :  "[INFO] The CCD Temperature is 16.700. "
[2021-09-20T21:04:54.656 MDT INFO ][           org.kde.kstars.indi] - ZWO CCD ASI290MM Mini :  "[INFO] Loading device configuration... "
[2021-09-20T21:04:54.656 MDT INFO ][           org.kde.kstars.indi] - ZWO CCD ASI290MM Mini :  "[INFO] Upload settings set to client only. "
[2021-09-20T21:04:54.663 MDT INFO ][           org.kde.kstars.indi] - ZWO CCD ASI290MM Mini :  "[INFO] Device configuration applied. "
[2021-09-20T21:05:06.824 MDT INFO ][   org.kde.kstars.ekos.capture] - Dithering succeeded, capture state "Dithering"
[2021-09-20T21:05:06.824 MDT INFO ][   org.kde.kstars.ekos.capture] - "Dithering succeeded."
[2021-09-20T21:05:06.824 MDT INFO ][   org.kde.kstars.ekos.capture] - "Dither complete. Resuming in 3 seconds..."
[2021-09-20T21:05:06.825 MDT INFO ][     org.kde.kstars.ekos.guide] - "Dithering completed successfully."
[2021-09-20T21:05:06.830 MDT INFO ][     org.kde.kstars.ekos.guide] - "Guiding resumed."

I have turned on verbose loggin for guiding and will see if I get another instance

It's been noted in the original thread that the camera freeze has been seen without dark subtraction. It is entirely possible these are separate things that just happened to coincide.

I did not get a freeze overnight so no verbose log yet.

As posted in another thread, here two log snippets that show the freeze (guide cam timeout):

At 23:25:58 the guide graph got stuck for the first time. The logfile reports:
[2021-09-08T23:25:26.309 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] BLOB transfer took 0.0880408 seconds "
[2021-09-08T23:25:26.310 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] Upload complete "
[2021-09-08T23:25:26.667 CEST DEBG ][           org.kde.kstars.indi] - Image received. Mode: "Guide" Size: 23397120
[2021-09-08T23:25:26.667 CEST DEBG ][           org.kde.kstars.fits] - Reading file buffer ( "22,3 MiB" )
[2021-09-08T23:25:26.893 CEST DEBG ][           org.kde.kstars.fits] - Sextract with:  "1-Guide-Default"
[2021-09-08T23:25:27.315 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] StartExposure->setexp : 1.500s "
[2021-09-08T23:25:29.870 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] Uploading file. Ext: fits, Size: 23397120, sendImage? Yes, saveImage? No "
[2021-09-08T23:25:30.003 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] BLOB transfer took 0.0902875 seconds "
[2021-09-08T23:25:30.003 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] Upload complete "
[2021-09-08T23:25:30.385 CEST DEBG ][           org.kde.kstars.indi] - Image received. Mode: "Guide" Size: 23397120
[2021-09-08T23:25:30.385 CEST DEBG ][           org.kde.kstars.fits] - Reading file buffer ( "22,3 MiB" )
[2021-09-08T23:25:58.954 CEST INFO ][     org.kde.kstars.ekos.guide] - <strong>"Exposure timeout. Restarting exposure..."    </strong>            [ <- no idea why]
[2021-09-08T23:25:58.959 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] Aborting exposure... "
[2021-09-08T23:25:58.959 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] StartExposure->setexp : 1.500s "
[2021-09-08T23:26:01.506 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] Uploading file. Ext: fits, Size: 23397120, sendImage? Yes, saveImage? No "
[2021-09-08T23:26:01.637 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] BLOB transfer took 0.0886794 seconds "
[2021-09-08T23:26:01.637 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] Upload complete "
[2021-09-08T23:26:01.994 CEST DEBG ][           org.kde.kstars.indi] - Image received. Mode: "Guide" Size: 23397120
[2021-09-08T23:26:01.995 CEST DEBG ][           org.kde.kstars.fits] - Reading file buffer ( "22,3 MiB" )
<strong>[2021-09-08T23:26:08.405 CEST DEBG ][   org.kde.kstars.ekos.capture] - Guiding state changed from "Guiding" to "Aborted"
[2021-09-08T23:26:08.407 CEST INFO ][     org.kde.kstars.ekos.guide] - "Autoguiding aborted."
[2021-09-08T23:26:13.580 CEST DEBG ][   org.kde.kstars.ekos.capture] - Guiding state changed from "Aborted" to "Guiding"    [<-- </strong>since the guide graph didn't move anymore, I stopped and re-started guiding. The guider did work without problems then...]
[2021-09-08T23:26:13.588 CEST INFO ][     org.kde.kstars.ekos.guide] - "Autoguiding started."
[2021-09-08T23:26:13.596 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] StartExposure->setexp : 1.500s "
[2021-09-08T23:26:16.148 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] Uploading file. Ext: fits, Size: 23397120, sendImage? Yes, saveImage? No "
[2021-09-08T23:26:16.283 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] BLOB transfer took 0.0905578 seconds "
[2021-09-08T23:26:16.283 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] Upload complete "
[2021-09-08T23:26:16.633 CEST DEBG ][           org.kde.kstars.indi] - Image received. Mode: "Guide" Size: 23397120
[2021-09-08T23:26:16.633 CEST DEBG ][           org.kde.kstars.fits] - Reading file buffer ( "22,3 MiB" )
[2021-09-08T23:26:16.843 CEST DEBG ][           org.kde.kstars.fits] - Sextract with:  "1-Guide-Default"
[2021-09-08T23:26:17.280 CEST DEBG ][           org.kde.kstars.fits] - Sextract with:  "1-Guide-Default"
[2021-09-08T23:26:17.520 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] StartExposure->setexp : 1.500s "





Another freeze happened later during the same night:
[2021-09-09T02:01:12.953 CEST INFO ][     org.kde.kstars.ekos.guide] - "Exposure timeout. Restarting exposure..."
[2021-09-09T02:01:12.958 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] Aborting exposure... "
[2021-09-09T02:01:12.958 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] StartExposure->setexp : 1.500s "
[2021-09-09T02:01:15.507 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] Uploading file. Ext: fits, Size: 23397120, sendImage? Yes, saveImage? No "
[2021-09-09T02:01:15.637 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] BLOB transfer took 0.0875795 seconds "
[2021-09-09T02:01:15.637 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC : "[DEBUG] Upload complete "
[2021-09-09T02:01:15.986 CEST DEBG ][           org.kde.kstars.indi] - Image received. Mode: "Guide" Size: 23397120
[2021-09-09T02:01:15.986 CEST DEBG ][           org.kde.kstars.fits] - Reading file buffer ( "22,3 MiB" )
.
no entry for 26s! The guide graph did not update (as no further guide images were received).  This time I did not interrupt but waited for what happens. Once the 300s image from the main cam had downloaded, dithering and guiding resumed normally but the image received from the main cam had a HFR of 1.9 which indicates that guiding did not work during these 26s.
.
[2021-09-09T02:01:41.287 CEST INFO ][           org.kde.kstars.indi] - ZWO CCD ASI294MC Pro :  "[INFO] Exposure done, downloading image... "
[2021-09-09T02:01:41.308 CEST INFO ][           org.kde.kstars.indi] - ZWO CCD ASI294MC Pro :  "[INFO] Download complete. "
[2021-09-09T02:01:41.340 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC Pro : "[DEBUG] Uploading file. Ext: fits, Size: 23397120, sendImage? Yes, saveImage? No "
[2021-09-09T02:01:41.471 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC Pro : "[DEBUG] BLOB transfer took 0.0878639 seconds "
[2021-09-09T02:01:41.471 CEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI294MC Pro : "[DEBUG] Upload complete "
[2021-09-09T02:01:41.821 CEST DEBG ][           org.kde.kstars.indi] - Image received. Mode: "Normal" Size: 23397120
[2021-09-09T02:01:41.829 CEST INFO ][           org.kde.kstars.indi] - "FITS" file saved to "/home/trifid/Bilder/heute/Light/Helix_Light_300_secs_2021-09-09T02-01-41_025.fits"
[2021-09-09T02:01:41.829 CEST DEBG ][           org.kde.kstars.fits] - Reading file buffer ( "22,3 MiB" )
[2021-09-09T02:01:42.006 CEST INFO ][   org.kde.kstars.ekos.capture] - "Download Time: 0.53 s, New Download Time Estimate: 0.57 s."
[2021-09-09T02:01:42.144 CEST DEBG ][           org.kde.kstars.fits] - Started WCS Data Processing...
[2021-09-09T02:01:42.144 CEST DEBG ][           org.kde.kstars.fits] - Finished WCS Data processing...
[2021-09-09T02:01:42.178 CEST INFO ][   org.kde.kstars.ekos.capture] - "Received image 18 out of 30."
[2021-09-09T02:01:42.182 CEST INFO ][   org.kde.kstars.ekos.capture] - Dithering...
[2021-09-09T02:01:42.182 CEST INFO ][   org.kde.kstars.ekos.capture] - "Dithering..."
[2021-09-09T02:01:42.182 CEST DEBG ][   org.kde.kstars.ekos.capture] - Guiding state changed from "Guiding" to "Dithering"
[2021-09-09T02:01:42.184 CEST INFO ][     org.kde.kstars.ekos.guide] - "Dithering in progress."
[2021-09-09T02:01:42.663 CEST DEBG ][           org.kde.kstars.fits] - Sextract with:  "1-HFR-Default"
[2021-09-09T02:01:42.829 CEST DEBG ][           org.kde.kstars.fits] - FITS HFR: 1.90059
... nothing happens for 26s ... this time I did not interrupt but waited. once the 300s frame from the main cam is received,
[2021-09-09T02:01:41.287 CEST INFO ][           org.kde.kstars.indi] - ZWO CCD ASI294MC Pro :  "[INFO] Exposure done, downloading image... "

The full log is attached.

I got a verbose log for ccd with guide freeze:

[2021-10-03T20:01:46.420 MDT DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI290MM Mini : "[DEBUG] Uploading file. Ext: fits, Size: 4250880, sendImage? Yes, saveImage? No "
[2021-10-03T20:01:46.428 MDT DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI290MM Mini : "[DEBUG] BLOB transfer took 0.00723282 seconds "
[2021-10-03T20:01:46.428 MDT DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI290MM Mini : "[DEBUG] Upload complete "
[2021-10-03T20:01:46.445 MDT DEBG ][           org.kde.kstars.indi] - Image received. Mode: "Guide" Size: 4250880
[2021-10-03T20:02:16.358 MDT INFO ][     org.kde.kstars.ekos.guide] - "Exposure timeout. Restarting exposure..."
[2021-10-03T20:02:16.360 MDT DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI290MM Mini : "[DEBUG] Aborting exposure... "
[2021-10-03T20:02:16.362 MDT DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI290MM Mini : "[DEBUG] StartExposure->setexp : 0.500s "
[2021-10-03T20:02:17.471 MDT DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI290MM Mini : "[DEBUG] Uploading file. Ext: fits, Size: 4250880, sendImage? Yes, saveImage? No "
[2021-10-03T20:02:17.477 MDT DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI290MM Mini : "[DEBUG] BLOB transfer took 0.00551742 seconds "
[2021-10-03T20:02:17.477 MDT DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI290MM Mini : "[DEBUG] Upload complete "
[2021-10-03T20:02:17.494 MDT DEBG ][           org.kde.kstars.indi] - Image received. Mode: "Guide" Size: 4250880
[2021-10-03T20:02:47.358 MDT DEBG ][           org.kde.kstars.indi] - Removing managed driver "ZWO CCD"
[2021-10-03T20:02:47.358 MDT DEBG ][           org.kde.kstars.indi] - INDIListener: Removing device "ZWO CCD ASI290MM Mini"
[2021-10-03T20:02:47.359 MDT INFO ][           org.kde.kstars.ekos] - "ZWO CCD ASI290MM Mini is offline."
[2021-10-03T20:02:47.360 MDT DEBG ][           org.kde.kstars.indi] - Stopping INDI Driver 

Can you confirm if this is an issue ONLY when dark is checked?

I think the dark thing may be a coincidence - since it  first happened I have stopped using dark subtraction and it did occur again, the log above was without dark subtraction.  Probably a driver or usb issue.

It happened to me many times despite the fact that I never use dark subtraction.

It's happening to me too without dark subtraction on an ASI120MM and latest version of KStars (3.5.6 Beta):
2021-10-04T20:21:38 Exposure timeout. Restarting exposure...
2021-10-04T20:19:45 DEC swap enabled.
2021-10-04T20:19:45 Autoguiding started.
2021-10-04T20:19:45 Calibration completed.

Can someone test with another algorithm (Smart for example). I suspect this is SEP star detection issue.

Never mind, can someone test this simple change? in guide.cpp, change line 446 from:
to
and check if this makes any difference?

Last night I tested the new code and did not witness any guide cam timeouts. However, this was just a few hours of guiding and it would be premature to sound the all-clear horn already. We need more testing IMO.

Same here, compiled a new version (linux x64) with the line changed and it's been running for 2h without problems.
But maybe its too soon to say it's safe. One thing I noticed is that there is an extra very small delay every 2 frames (1 second frames).
 

Encouraging but it does need a while to be sure. I have gone a couple of nights without freezes only to encounter several in the space of an hour.