I have been having problems with several cars (N scale) and one loco (4664 Challanger) derailing at one turnout. I checked the wheels using my guage and everything checked out fine, still the problem persisted. I then got out my digital caliper and checked the wheels again and some were off just a hair. After some small adjustments I have no more derailments. The NMRA guage is not as accurate as one would think.
Any chance it wasn’t the gauge? Sometimes there are sharp points on the turnout where they file the main track where the point merges. Flanges will sometimes catch it.
Yes, a good question. I would suspect the gauge of the turnout, particularly the guards, first. The NMRA gauge is pretty darned solid AFAIAC.
-Crandell