Since release 1.5.1 vehicle are "jumping" every few seconds (seems to be every 3 seconds), even when on flat land. Not high, but high enough to irritate the player. The jumping stops when the player enters the vehicle, after leaving the vehicle the jumping starts again.
I noticed kind of the same behavior at planes, they don't jump, they spin few degrees and back.

It looks like the model is look for the correct position or checking he position on the ground.

Should be fixed by this point thanks to flan's hard work on physics

Not only vehicles but also AA turrets... whenever i place it, it just bounce bounce bounce....