This is an engine that I looked at a few years ago and after poking around and trying an R4LC board, it started running normally. When I looked at it before, it was running erratically. And at the time I only had an S01 radio board which was no test at all. I have an S03 board now and no luck with that.
GRJ suggested that the most likely suspect is the motor drive board and since the motor ran before (but erratically), I guess I can eliminate the motor. That leaves the motor sensor board and the motor drive board...I guess.