First never use steel wool around toy trains it gets tangled in their guts. I'll say that before something breaks, I learned that from some who killed an engine with it.
I have a similar issue with the Lionel fas-track version of the 90 degree crossing, and derailment issues with manual O-36 switches. Sounds like a misaligned joint and possibly the roller getting temporary stuck in the engine, moving it would jar it free, oil it? Also I have found carpet can cause alignment issues, not bad ones, but the deeper the carpet the greater the problem. (Old carpet tends to wear into a mix making it easier to see)