See here...
Weight matters
The problem is in this hole.
Good thing the masonry is removable.
See in there where the feeder wires are? I guess I melted the tie plates because the rails had "come together" (Beatles) which was causing some RS & loco wheels to be forced over the outside rail.
A little "adjustment" with needle-nose pliers and all is good now.
But it'll happen again. So it's decision time. Try pouring some epoxy or some such in there to make the rails stay, or cut the top off of the mesa and re-lay that section.
Damn, I thought the underground track was bullet proof.