Thanks for all the great info guys! My layout is quite modest, only a 10’ X 16’ X 16’ U shape. I was able to camouflage the ground plane wire under the upper level, which is directly above the problem areas noted earlier.
I’m inclined to think it’s the particular locomotive, as my other TMCC engine has no issues whatsoever anywhere on the layout.
I didn’t realize winding an antenna several times around a locomotive’s insides would work, and I’ll add that later this week. The foot long copper rod I soldered to the capital I shaped “reflector” antenna is ok, and fits within the shell-but only just barely.