I was playing normal and I close the game, I bought The tanks and helicopters DLC and I open again the game, after that in every vehicle I'm boarding me and the other players are standing strait with the weapons out, in the middle of the vehicle or in the side, If you are the driver wen the vehicle move the player model walks too, no mods, new install. That for me only, doesn't happened to the other players, it happens everywhere, SP MP VR