[TM Pilot]

That the grounding points on your TV were corroded and causing the low voltage instead of the grounding points on the TM makes sense since the TM battery didn't charge via the TV but did charge when connected to shore power.

Low voltage is often caused by a corroded ground, therefore it is a good place to start the troubleshooting process. My electric tongue jack stopped working because of low voltage due to a corroded ground through my swing hitch. Once I cleaned it, it worked great.

Good work, John! Glad your TM issues have been resolved. And nice catch on the breakaway cable power lead. Having a fully charged battery while towing wouldn't mean a thing during a breakaway if the power lead is disconnected! Looks like your charging issue was a blessing in disguise.