[idroveatrain]

It can happen on straightrail on an incline, too. It's hard to assess precisely what's happening in the locomotive, but under traction I believe the running gear will toe out, and align based on the path of least resistance. I believe this leads to the flange pressing, with immense force, against the rail. You also get a lot of wheel slip in this condition.

I surmised this running 2 motors up a 3%(?) grade with 20k ton gross at 10mph. It's about the only explanation I could come up with is that the running gear was twisting under the gravity and the energy being put down to work against it. It might also just be a stringline sort of effect dragging the motors to one side of the track and pressing the flange. Maybe one of the rail engineers will come holler at me for my poor trainhandling skills.