Given that you only run conventional, a "board reset" is cycling power. 
The one that the sounds continue on has the earmarks of a board failure, there is a failure mode where the board won't shutdown until the battery is removed.
Swap the RailSounds boards between the two units, one at a time. You should be able to isolate the issue if it's a board failure.
The powered B-Unit sounds like either a board failure or perhaps just a loose wire issue. Have you opened it up and checked for any loose wiring?
How about actual models for each of these units?
You know that TMCC doesn't charge the battery, so a "battery eliminator" needs the charging circuit as well as the supercap package, right?
