Ok, it may be signal issue, then. TMCC actually puts signal on the "earth" wire in your home wiring, so your home becomes a TMCC antenna. This is the signal the engine has to 'see' in order to operate. Too much metal between the house wiring and the train can interfere with the train's ability to pick up the signal. This might be what is happening in your chicken wire tunnel. You may be able to fix it by running a wire connected to earth (not to the track ground) into the tunnel, or connecting the chicken wire to earth, so the tunnel itself becomes part of the TMCC system. I'm sorry I can't give you more specifics because I have not had this problem myself, but I remember it being discussed quite a lot here at one time. (The closest I ever came is when we parked a certain large, die-cast engine in a certain spot that had another track underneath it. Trains on the lower track would lose TMCC. Rather than re-wiring, we just didn't park that engine there anymore!)
Search the forum for "TMCC" and "ground plane" to learn more.
That's assuming your other trains go thru that section alright. If nothing makes it through, it is probably a loss of power problem.
