I ran into that once, a few patches ago...and it looked that way to both me and another guy nearby, so it may actually be in the system.
Was overflying a strat, and the rail line ran down a hill into the strat valley. We both saw the train keep going straight instead of down... which made the flak rather, umm, interesting. Fortunately the train hooked up with its station and disappeared into the strat not long after.
Was pretty amusing though.