Layout help. Please

[Charlie B]

When you say short, do you mean when the switches are thrown to diverging, or when the train actually enters the track? if all the other track is OK when the switches are thrown look for a problem with the switches. Try throwing only one switch and see if you can enter the track with a train (from either switch). That will give you some place to start. It all appears OK as far as no reverse loop to cause a short, so if there is a short it may be in one of the frogs. Are the switches power routing?
Sometimes that causes a problem.
Charlie