I noticed all kinds of autopilot issues when I switched from having the full TDS setup to a radio-only aircraft with dual kx155B. Could engage flight director and autopilot but things went a bit weir from there.
Couldn't get the altitude and rate to work properly
HDG, ALT, and NAV wouldn't illuminate on the KFC 150
While I could get it to hold altitude and get heading to work, nothing illuminated on the 150.
I tried swapping radios then going back but nothing consistently worked. I think I got it to work properly 1x out of the last 5 flights. Restarting flight didn't fix.
When doing an AP test, the yoke would turn right despite the heading bug set straight ahead, and trim would go full up despite altitude not being engaged.