yes, I've noticed it too:
it is 1391x1039 now, but it is not a deviation from the previous versions of Ekos and or Indilib. I have dark images captured by Ekos from 2014 that have the same 1391x1039 frame size. I had problems with the frame size being 1392x1040 when I captured flats using APT.
On 383L+ the frame size changed as well to match what Windows tools give, 3326x2504 to 3362x2537 so had to redo calibration frames. There are a couple of rough edges, temperature reading seems to interfere with image download but adding a mutex there fixed it. Another thing is that subframing is not enabled on my camera as the driver is checking for a capability which presumably means something else, but enabling the capability unconditionally fixed this too.
Mine is 383L+ too.
I've notice the same behavior with sub-framing not allowed while testing auto-focus.
I believe that donwload time get slower too, but maybe it's only a "felling", I don't have numbers to compare.
I compare the time need to take a bias with a previous session log and it is not slower. From old log 4.6 s, from new log 4.5 s. This is total time from start of exposure until the file is saved by the client.
Ok so subframing issue is confirmed. There is "preview" mode which I didn't enable. At any rate, if the camera supports preview mode, then it would be faster, but Ekos has no idea about this and it must be set from INDI control panel before you start focusing..etc.
Good, I noticed the issue when taking new calibration frames, around every 8-10th frame would time out downloading. 383L+ has larger frames so it takes longer and the window for race condition is thus much larger. But with the fix I got the calibration frames all taken and imaged a couple of nights without problems.
When first open focuser tab with Atik, the subframe is disabled "but" with a check-mark (I think this check is disconsidered when disabled, but I don't know). Then I selected the guider camera, that enable the box. It comes "selected", I unselect and switch back to Atik. Then Atik show the box disabled but unselected.
I didn't find the "preview" mode that need to be set in INDI Control Panel. It should be there?
The last picture is from Ekos, nothing to set there too.
I think that you are talking about an "internal" set that need to be checked on driver, not on visual interface (maybe I misunderstood).
I saw people talking about "mutex", is it something that I can "configure" ou it's a code change?
And the last thing, Jpaana says that 383L+ shows frame size as 3362x2537, in my case, same camera, 3354x2529 (firmware 801).
Subframing is enabled now with the update merged today, also the mutex is there, both are code changes and nothing to configure as such. My camera is using firmware 795 so the resolution seems to change between versions.