Update: i flew again the citation today: You can not have a/t on for longer. It disables itself so so so often. Today I thought, I have seen a warning message in the pfd of the g5000 in the moment A/T disabled itself. It was away before I could read it.
I am not sure if it is a symptom of the avionic crashes we see on PS5 regularly:
https://forums.flightsimulator.com/t/vision-jet-g3000-avionics-map-instability-on-ps5
Or
https://forums.flightsimulator.com/t/g1000-crashes-reboots-regularly
This needs to be fixed desparetly. A/T is not useable on all planes I tested. I edited the original post to reflect the newest information on that issue.