Pretty huge bug in my last session, Everyone is running in place.. Arthur can only go one step at a time.
Video proof, not sure if it's a CH issue or R* one...
Link
Are you using a feature that modifies your run speed? The threading in RDR is a bit mangled in my experience which may be the cause of your issue. Are you able to repeat the "bug" confidently?
Generally speaking running in place is unlikely to be caused (at least directly) by a trainer. That doesn't mean the trainer may not be contributing to an already unstable threading environment - But that's on Rockstar. Are you running on an i5 CPU?