My autopilot is now functioning as expected under almost all circumstances. However, I still have a problem where the plane will sometimes dive below glidepath partway through a fully coupled approach. Min Airspeed is set to 70 on my AFS5600, which I have triple-verified after my previous error above, and I've confirmed through flight logs that my actual airspeed was well above that minimum (I saw 76 knots minimum in my log for the most recent approach where this occurred).

After experimenting with this at altitude in slow flight, flaps-down configuration (normal behavior observed) and then on multiple approaches (where the plane sometimes but not always dives below glideslope), I have a theory. I believe this is due to the aircraft being out of trim, and the autopilot not being able to overpower the out-of-trim condition. On my last flight, I was on glideslope to KPWT on ILS 20 approach with autopilot on and properly tracking glideslope on final. Then about 1/2 way down final, it started to dive below glidepath with autopilot still engaged. I disengaged autopilot and could feel that the stick was pretty heavy in the forward trim state. I'm sure that's because I had trimmed for cruise on my way to KPWT and did not re-trim when I slowed down and lowered flaps on final. After taking control from autopilot, I trimmed the plane correctly, leveled off and re-engaged the autopilot, which then correctly followed glideslope again. This strongly suggests to me that this is an out-of-trim problem, although I don't recall feeling any servo slippage from the autopilot before it dived below glideslope, which seems odd. Have you seen any other issues where the autopilot can't overcome an out-of-trim condition?

Related to this... I have searched multiple AFS and Skyview manuals trying to find out whether the AFS5600 displays any sort of "out of trim" indicator when autopilot is on. It doesn't appear so. There is one mention of a "pitch slip alert" in the Pilot's guide, but no mention of how I enable that or see it anywhere. Maybe it is an audible?? Don't know. Let me know if I'm missing that somewhere.