There is a history of Lionel Fastrack remote track-switches sometimes having their terminal blocks assembled incorrectly at the factory. Any time there is an issue it is best to start with checking this out. Take the bottom cover off the offending switch and check that the wire yellow wire from the "AUX GND" terminal goes to an outer rail jumper-bar. "AUX IN" should go to the circuit board (this red wire has a fuse in it hidden under a bit of shrink-tubing) and "TRACK JUMPER" to the center-rail jumper-bar.
The terminal block is actually three single terminals assembled together:
If found in an incorrect order the terminal block can be easily assembled correctly.