Earlier on the custom map testserver I experienced something similar to the backwards arty bug (since fixed). I was comm, and built a BE tank via the VF. When it spawned, the turret was facing the rear of the factory. As soon as I got in the tank, it returned to normal. I am assuming that this is because without a player inside the turret does not get its position initially set? Maybe could affect other vehicles? I haven't attempted to reproduce this bug.
its the same with tanks, but it actually looks cool when a soldier enters a med tank and its turret turns 180 degrees to the correct position, most of the time it jumps straight to the correct position but ive seen it do the funky rotation a few times and it looks cool :D