I've left a comment on the main page about this but i'm sure it will get buried before long, hell it might already be as you're reading this so i'm gonna also make a discussion so this can stay fresh... er.

So anyway you can place your locomotive and a few train cars and all is good but after a while the bogeys lose their ability to rotate, while you're going straight it's fine but as soon as you reach a curve the loco will act almost as if you crashed into a wall, i then was unable to rerail the locomotive because the bogeys didn't rotate and it wouldn't fit in the rail like that, if anyone knows of a way to fix this please let me know.(of course i'd prefer it to be fixed in the addon itself)

EDIT: I've been doing some testing and apparently the bogeys were locked from the start, i just didn't go into a curve that was sharp enough for it to be an issue and not all locos/traincars have this issue. It seems to be mostly the bigger diesels that have locked bogeys, some railcars do get their bogeys locked after a while but i haven't found any consistency.