Mark, I wonder if the results would be the same if you set the power selector from ground power to APU, and from Batt to STBY.

Also, I thought mine was fixed but then I remembered that I had added
electric_always_available=1

So when I removed it the problem arose again.

I think one reason more people haven't posted this problem is most people probably start the APU and start engines and fly. But some of us spend quite a bit more time on the ground on APU power, enough time for the electrical problem to appear.