Not computers, but you folks are probably pretty smart.

[TexasProgresive]

2. First you did a great job of troubleshooting.

With any device with multiple parts it often is a process of elimination. As to your question, this is a guess as I can't put my hands on it, but I believe that there is an incomplete short circuit in that one piece of track. If it was a complete short nothing would work and it it might trip an internal circuit breaker on the power source.

It's been a long time since I handled electric train parts so I can't remember how the power is passed from one piece of track to the next. If I had it and a known good one in hand I would use my ohm meter to measure for the short. I doubt that piece can be effectivly repaired.

I am surprised that there isn't an electric train forum on DU. My far distant brothers-in-law are train nuts with great layouts in their basements.