Maybe try spraying just the pilot wheels with some of the new aerosol nickle silver Magna Traction??
Watch real close while someone else powers the engine over the site.
Try running real slow while carefully watching.
Manually push the engine's pilots wheels off the end of a piece of track with no pins at the edge of a table. Do both wheels hang level?
Any derailment turning the engine around and run in the same East/West direction?
Fast tracks can have a rail head leaning sideways just enough to catch a lightly sprung pilot wheel.
If you have a derailment with three rail equipment there is an obvious gremlin.
Replace the two track sections at the point of trouble.
Is the curve's right of way truly correct geometrically. ( I have seen some folks use too many or too few degrees of track section combinations for the curve desired). Just because one can kinda fudge slide the track together does not mean it is correctly assembled.
Most of all, relax, this problem is a pain but simple to correct.
