51112 HO 4-4-0 pilot truck derail

[railroadnut]

I go back a ways in MRR (built an HO some years ago with my dad) and have designed (but not yet build) an N layout (have collected all materials over several years). I recently purchased the 51112 for an under tree "Christmas village". but after several days of operation, the inevitable fuzz collected and locked up the worm gear. I disassembled, cleaned and reassembled. Now there is significant wobble in the loco and the pilot truck wants to derail. There seems to be some misalignment between the driver gear box and the boiler, but I can't seem to see anyway to straighten it. Funny thing, it only derails running counterclockwise, not clockwise. Min radius is 18" with one section 22". Derails on both curves.
Any ideas?

Thanks   

[ABC]

Don't run it on carpet in the future, and beg Bachmann for a new one if otherwise under warranty.