I just published libqhy v21.10.26 and it should be in the nightlies. You can try that, not sure if they fixed this particular issue since then.

I saved the geometry dimensions manually and it worked. Until I stop the exposure. The camera hangs and it disapears from the usb bus.
You have to disconnect it from the usb port and connect again. Try with the libqhy that Jasem put on the ppa. That was the last version I tried
and it did not solve the problems. Maybe you are luckier than me.

Thanks to both of you, I will try the nightly.

Have anyone presented the problem to QHY? I guess its a driver problem?

I think the problem is really on the linux SDK as the older version (wich I don't remember) on my RPi3 worked without any problems.
I am also using it with Windows (ASCOM and Native) and I don't have any problems with it so I know the problem is not the camera itself.
Maybe this issue came up on the very old qhy forum some time ago, but I dont think it was solved or even answered.

Yeah, my camera worked perfectly. Then i updated Indi+kstars and it gave this error.

I will write to qhy if the nightly does not fix the problem.

I have just tried my QHY6 with the latest updates and this is the new status:

1 - Resolution is still missing from the driver so I have to save it manually on INDI Panel.
2 - Capture module captures just fine, any exposure.
3 - Focus module works with still pictures and looping. If I stop looping in focus module the camera hangs after 3 ou 4 cycles of start-stop looping. .
3 - Guiding module works partially, still pictures work. Looping starts working but has soon as I stop it, the camera hangs and it's no longer available.

But.... the latest libqhy (both  libqhy_21.10.26 unstable~202110262312~ubuntu21.04.1_amd64.deb  and  libqhy_21.10.26 unstable~202110262315~ubuntu21.10.1_amd64.deb  ) still includes 21.9.10 and not the 21.10.12 (latest)?
Anyway I have downloaded and installed the latest SDK and the results are the same as above, so no solution yet. 

I tried the nightly and it still give me this error

How did you manually set the values?

On the indi panel, image settings tab. Fill the values and save.
 

752x582 for usable field resolution or 800x596 for full resolution.
After saving this values it won't give an error anymore. 
But you have to do it everytime the libqhy sdk gets updated.
 

Ah ok, I already have those set but I still get the errors...

Did you save the camera options?
I don't have errors now, where are you seeing yours?

Ok I have just saw them. They only appear when the camera is in loop mode, in still mode you don't get them:

2021-10-28T19:01:42: [ERROR] Invalid frame requested (0,0) (0 x 0)
2021-10-28T19:01:34: [INFO] Exposure aborted.
2021-10-28T19:00:58: [ERROR] Invalid frame requested (0,0) (0 x 0)
2021-10-28T19:00:57: [ERROR] Invalid frame requested (0,0) (0 x 0)
2021-10-28T19:00:56: [ERROR] Invalid frame requested (0,0) (0 x 0)
2021-10-28T19:00:55: [ERROR] Invalid frame requested (0,0) (0 x 0)
2021-10-28T19:00:54: [ERROR] Invalid frame requested (0,0) (0 x 0)
2021-10-28T19:00:20: [ERROR] Invalid frame requested (0,0) (0 x 0)
2021-10-28T19:00:19: [ERROR] Invalid frame requested (0,0) (0 x 0)
2021-10-28T18:59:44: [INFO] World Coordinate System is enabled.
2021-10-28T18:59:44: [INFO] Device configuration applied.
2021-10-28T18:59:44: [INFO] USB Buffer updated to 512
2021-10-28T18:59:44: [INFO] Gain updated to 0
2021-10-28T18:59:44: [INFO] Upload settings set to client only.
2021-10-28T18:59:44: [INFO] Loading device configuration...
2021-10-28T18:59:44: [INFO] Offset Settings: Value: 140 Min: 0 Max: 255 Step 1
2021-10-28T18:59:44: [INFO] Gain Settings: Value: 0 Min: 0 Max: 63 Step 1
2021-10-28T18:59:44: [INFO] USB Speed Settings: Value: 1 Min: 0 Max: 1 Step 1
2021-10-28T18:59:44: [INFO] Humidity Support: False
2021-10-28T18:59:44: [INFO] Camera exposure limits: Min: 0.001000s Max: 3600s Step 0s
2021-10-28T18:59:44: [INFO] Sensor resolution for mode STANDARD MODE: 800x596 px
2021-10-28T18:59:44: [INFO] Mode 0: STANDARD MODE
2021-10-28T18:59:44: [INFO] Using QHY SDK version 21.10.26
2021-10-28T18:59:44: [INFO] Connected to QHY6-M-0106XXXXXXXXXXXX.

Yes, those I also get! Additionally I get "The calculated field of view is out of bounds" error and it seems that indi is not calculating the focal length from the plate solved image.

I think I will try to write QHY, it seems to be their issue....