Yesterday, the AF-5500 was commanding the autopilot based on heading and altitude bug settings.
During descent in mild turbulence the EFIS stopped commanding the autopilot so the autopilot
reverted to track mode and altitude hold. There was also an annunciation that I missed because
I was listening to ATC at the time but the first word was "autopilot" and I missed the second word.
Can you tell me the cause of the reversion to autopilot control or tell me what to watch for in case
it happens again?

After I used the autopilot disconnect switch on the stick and reset the commands on the EFIS it
commanded the autopilot as expected for the remainder of the flight (roughly 20 more minutes).

AF-5500 with engine board (but no engine sensors yet), GPSMAP 396, SL-30, AF-Pilot, AF-ARINC,
in a Cozy III.