Thanks everybody for your help and advice.
While waiting for the new library to show up in git, I manually updated it in my installation and all problems are gone.
The new library also seems to handle errors in a much better and robust way than before.
The hardware check doesn't show any possible problem.
Furthermore, I tested the wheel by attaching it to a RasPi running Indigo Sky and it works like a charm, no freezes or locks or hangs whatsoever.
On the other hand, it seems I'm the only one having this problem with the ZWO EFW and INDI (can't find much by googling) so I'm more and more puzzled...
Bart, thank you very much for your suggestion.
I'll make a thorough hardware check and let you know.
I forgot to mention that I made further testing at home and it continues to happen, randomly: it can hang at the first filter change, after 2 or 5 or 10 or 20 changes and so on.
recently I started having problems with my 5-position ZWO EFW.
Everything used to work fine until the last time I went under the stars. On that occasion, the following morning I found out with surprise that, after a certain moment in the photo session, the EFW had stopped working silently.
The capture software (CCDciel) sent the commands to the wheel and showed as if the filter had changed, but actually it had not, so I ended up the whole photo session with all frames (more than 1000) only in the red channel
The problem is that it happens silently, the efw indi driver hangs and no error messages come from it, it just hangs and I have to kill it manually because also indiserver seems to lose control over it.
Has it happened to someone else? Is there a way I can send more information to investigate this issue deeper?
Never mind, in the meantime I've upgraded my 16.04 to 18.04 and all is fixed
Oops, spoke too soon...
Package indi-full is not upgradable because the indi-aok dependency is missing
This morning it seems to have been fixed in the stable too.
Forgot to say that I'm on the stable builds.
Have you solved this issue?
I'm too on Astroberry (Ubuntu 16.04) and still can't find the package.
last night I had the chance to finally test Ekos and its polar alignment procedure.
I had problems with it because when moving the mount (iOptron SmartEQ Pro) for the first rotation Ekos parked the mount instead and then stopped.
I had to use the manual slew and then the procedure completed correctly (and quickly, I should say) leaving the mount perfectly aligned.
However, I also experienced a lot of crashes of Kstars/Ekos on my 64-bit Intel miniPC with Ubuntu 18.04: has anybody else experienced the same crash problems?
Ok, thanks Jasem