Your analysis makes perfect sense. It's probably a 10 minute fix for an expert. For me, the best solution is to have a Lionel techician make the repair.
I am trying hard to not allow glitches like this blow the wind out of my sails when it comes to the sport of OGR railroading.
When I first got the MTH DCS system, it had to go to MTH for a repair (it took six weeks). Even my Lionmaster Legacy Big Boy (which I purchased brand new) had a defective Odyssey control board.
Situations like this seems to come with the hobby. I have learned to cope with it. Now I get it when I read numerous posts about members who exclusively operate in conventional mode.
Despite the occasional problem, my passion for O scale railroading is stronger than ever.