Hi Larry,
Thanks for the quick reply and the welcome. I have two switches in this layout. I checked them both, and one may be the problem. I did a continuity check and found that on one switch the Aux In terminal connects to the center rail on the track (the Aux Gnd connects to the outer rail as expected). Oddly enough, on that switch the Track Jumper terminal doesn't connect to either rail. I'm guessing that the crosstalk came from here, with the Aux In taking power from the track to supply the lights. Does that make sense? Do I need to send the switch in for repair or is this a simple fix?

Also, thanks for the heads-up on phasing. I hadn't thought that one through enough. Fortunately I haven't connected up both transformers yet. I'll review the wiring to make sure both transformers are connected in parallel.

Leathem