I get OP Error and Invalid Consist on Norfolk Southern Coal District on this career scenario(ES44AC NS:Monumental Part 2)several times but it is only to resume the game again. When I get that error the locos also derails so I have to resume the scenario. Is that a well known bug? It is really anoying as the scenario is 80 min if I remember correct.
I have played this several times without this error. I have heard of several other bugs for this route but not this particular one. What is known is starting from a save will occasionally cause issues. One way to help prevent this is to always save while you are stopped and never with the red progress bar running.