Hi Vern
Seeing that Trainz don't know - or care for that matter 

 - the gauge at all of the track, I highly doubt that is the reason.
Maybe it is in the config for the track spline, maybe it is a programming difference in Trainz reading those particular configs in a different way then others, I don't know, but, you have made me a little curious though. 
 
Could this be related to a setting in the Region part of the route, I seem to recall in the older days we could put in a default lever in a Region asset, and then that was used for all junctions in the maps using that region.
Maybe the lever there is missing, or points to a kuid you don't have?
Jut guessing really. 
 
Best of luck figuring it out, I will keep and eye on this thread, hoping to learn some more about the inner workings of Trainz at least, thirsty for knowledge, or as I like to look at it, curious like a cat... LOL
Except I dislike the cat right now as she dragged a live bird in, and went on to catch it again inside the house...
In the end, she managed, took the tail of the bird, then the body, but, she left it on the floor, and I managed to put something on it, and we got the bird out, and it flew of so I think it went OK in the end. 
 
Take care
Linda