I think you may have a metal part, or newly bared metal part (scrapped paint, or chipped metal..?) from the derailment contacting the frame or boiler, or cylinder saddle..., not sure. One guy on the MR forums, goes by name cudaken, had no end of fits with his first Paragon Y6b after a few months of heavy running. He eventually found that the metal post pivot for the front engine had worn sufficiently that the cylinders, or something swinging with the front engine around curves, made bad contact with the locomotive's frame. He had to rebuild the pivot post, or use insulating washer material....can't recall.
If you can't get it to reset because of persistent shorts, you might want to call and ask to speak to a tech at BLI. He'll hopefull spend three minutes, talk you through some tests, and then maybe have to give you a return authorization.
I know this is a real bummer, but my first issue of Y6b from the same Paragon series as cudaken continues to work like a champ to this day. I did have to return it to BLI, but only once I dropped it and broke the mount for the front engine. Their repair was cheap, including return postage, and that was four years ago. Believe me, once you get one that runs, it will quickly attain a lofty status in your stable. It has no non-brass equal for pulling power in all the HO world for N. American types.
