You are correct that when turning main shaft by hand, we are not turning the motor. The motor drives a worm directly, which turns the gear on the main shaft, connected to the shaft by a ratchet. Thus, we have confirmed that the main shaft is not jammed, but the motor shaft may be jammed by a bad bearing or other manufacturing defect.

I think we have exhausted the possibilities until we discuss with Lofrans. Thanks partly to this board, I have lots of info to discuss with them.
The big question at the moment is how practical and reasonable or otherwise Lofrans warranty support is. We should get a start on that tomorrow. I already emailed Lofrans, and will be on the phone tomorrow

We have a 150 amp breaker now (Blue Sea model 187)
As I mentioned in another post, I think our measuring technique is OK, because it shows about 240 amps in our diesel starter motor. This does not trip a 200 amp breaker.
Remember that most breakers take a little time to trip if only marginally over the rated load