@BC1989 posted:Hi @Mixed Freight, thanks for the suggestion. This solution sounds sensible but I'm not exactly sure what you mean so I've attached a picture of the relevant switch. I think the frog is what I outlined in yellow. The red lines are the breaks in the rail, which I remember from my O-27 switches are insulated, so I assume that's where the frog ends (electrically speaking). Is the "straight anti-derail rail" what I've highlighted in green? Is that what I should try covering in tape?
Hey BC1989,
The frog is the yellow portion. The anti-derail rails are the rails just past the frog, with your red marks. These are the rails that you could tape over to test, and NOT the green rail.
That being said, this apparently is not your problem. Take a good look at your picture, and notice the point rails are set to the curved route. Now take an even better look at the curved route point rail that is supposed to be touching the straight stock rail. See the slight gap? This is your problem, there is not supposed to be a gap there at all. This tiny gap is letting the flanges of your pilot truck go on through the straight route and derail the front truck. Then the rear flanged drivers on the engine try and take the curved route, and total derailment ensues.
Something needs to be done to correct that slight gap at the points. As I don't own any Fastrack, I can't tell you for sure if there is an adjustment you can make, or if the switch is defective. At any rate, either way the switch is thrown, whichever point rail is guiding the train wheels to the proper route needs to be tight to the stock rail. A slight gap in the point rail will result in problems every time.
Either get that curved route point rail adjusted somehow or replace the switch one that has no gap for the thrown route and that should solve your problem. Hope this helps. 
