No nothing, is activated for focus/guide limits in the flat sequence.

Also, none of Track, Guide, Align, Focus or any contraint is checked in the schedule for the flat sequence.

Do you have the log files available? If yes, please post them. I currently do not understand why focusing gets stuck. Normally, focusing should abort after a certain amount of starless captures.

Sure, here's the tail of the log:  
Night-2021-11-18 is the flat sequence

It seems it isn't focusing, but that's the status displayed in the sequence tab. perhaps state machine is in the wrong state.

please post the entire log, it already starts weird. At 05:34:10.053 the scheduler starts focusing but the focuser answers with "Autofocus is already running, discarding start request." It seems like job IC_1805-Part3 had been in the focusing state and maybe this hasn't been aborted.

The scheduler file would also be helpful. What are your settings in the aborted job management?

Sure, many thanks for your help!
 

Same scheduler file incremented by one day. 
 

I was thinking I was being overly too agressive with immediate retry and 30s wait last week but forgot about it. I'll be changing that to 300s.

It looks like the problem starts at 04:50:31.395. Here focusing and aligning both try to access the camera. What I do not understand is, why the focus module gets active while alignment is running.

Do you have the autofocus option set on the Lum filter that it should focus on filter set? Because focusing starts directly before align reports "Changing filter to Lum..."

Yes I have autofocus checked for each filter. Also I remember checking "focus on filter change" somewhere, but couldn't find the option in current version.

Alignement is set to run using Lum filter and that night I was shooting Ha frames.

Hm, OK, there might be the source of the problem. I guess you also use the focus step in the scheduler job, right? If yes, which filter is set on the focuser tab?

Yes indeed I have focus checked for all targets/sequences but the flat one.
I am not sure I get your question, initially I have Lum set in the focuser tab, but it changes according to my sequence filter.

It looks like we have a concurrency issue here somewhere with autofocus on filter change and alignment. It looks like the filter change for alignment triggers a refocus, which from my perspective does not make sense.

But that’s speculation, one run of a similar scenario got stuck, the next run went smoothly.

I think your hypothesis is strong.

I have noticed that during alignment it switches filter sometimes. Sometimes before alignement, sometimes after, sometimes it focuses the "previous target" filter sometimes the Lum filter.

I think I found one reproductible case: Right after meridian flip is completed, it will do an alignment, followed by one focus on Lum and then a focus on target filter.
Another case I saw, when it doesn't manage to do focus, it seems to revert to focusing Lum filter at some point.

Perhaps this together with a concurrency lock could cause the issue I have.

I went through a few analysis files and could find one, with filter changing behavior:
 
 

and one with reverting to lum filter: