I'll break out the gauge but I am not optimistic. Here is how I trouble shooted the problem. Ranthe loco from west to east over the joiner and the front wheel derailed. After filing and scraping I ran it in reverse, east to west, over the joiner, no problem. Then I switched the direction of the loco and ran it forward east to west over the joiner and no problem. Running it in reverse, west to east, and there is a derailment.