Thanks for the speedy replies.
I would call it a hard shift, not a thump (I think).
I searched the archives with 'hard shift' and some of the 80 hits mentioned the electricality (neat word) of trannys and a vague description of a 'learn mode.'
I have not changed the chassis battery, but recall that I did just put in a new coach battery with a nice fresh 12.9 V charge. We turned the coach battery on for the mini-trip as we always do (not sure why, we were not using the coach).
Should I consider unhooking the chassis + batt terminal and thus resetting the computer?