The weird thing is neither part looks straight, but they match perfectly - either way round.
It is weird, but I can at least post them :-)

But I've definitely got an issue. did some sheriff's badges last night (going to cowboy themed meal wednesday) and the big one definitely had some offset layers.
Have to check the pulleys on the steppers. Can't think what else it could be.
I'll lock the motors and see if any of the belts still move.