RTL and crash after reaching home - 3.7.0?

Using APM Plane 3.7.0, I was flying a Skywalker 1800, had several flights on it with little drama. I had performed an autotune earlier in the day and all seemed good. I had tested all my modes: manual, fbwa, loiter, cruise, rtl , and auto/waypoints. All had been working, all programmed on two Taranis switches (3 position switches).

This last flight… I engaged RTL and the plane flew back to Home, but instead of loitering above home it started to veer to the west, NOT circle overhead. It also started pitching and rolling. Slowly at first, then more violently.

I had engaged RTL using a Throttle cut switch. I was in Cruise mode. Once the plane got to home and starting pitching/rolling I forgot I had used the Throttle cut switch to engage RTL. Instead I tried to use the other programmed switches to regain control, at least to Manual or FBWA. That had no effect on the mode as far as I could tell. The plane throttle climbed to 80% while this was happening, it hit the ground at 80% Thr.

If any of the Devs would mind looking at the lot it would be appreciated. I’ve built quite a few Pixhawk planes/copters and this is a first. The log seems to indicate it went back to Manual mode near the end, but the MP Telemetry Log, and in my DVR video it stays in RETL during this crash sequence.