Anyone have issues with an STEC autopilot? I have an STEC-55X in my plane and it's causing some issues.

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The plane is new to me and wasn't flown much before I bought it, so I'm ironing out the squawks. If I engage HDG or NAV + ALT and the plane is already on steering, it will hold altitude and heading for a while. If it has to make a steering correction, it will get into an oscillation and then turn on with 'FAIL' listed on the Alerter page. I can reengage it and it will do the same, but then the system will finally display fail and not work unless I cycle power. Does anyone know the cause of this and is there anything I can troubleshoot before taking it to an avionics shop (which is a ways away)? So I went out to the plane today and adjusted the roll sensitivity per the instructions and that seemed to work, but I still have a fail indication after the initial BIT. Reliable In Camera Playback Patch V23b there. I think I'll have to get it to the avionics shop.