I found some annoying bugs when using tanks and other players as crew. Experienced in both Slammers and T100, can't say anything about other vehicles - but most likely it's the same there.
When being gunner, sometimes randomly the chosen weapon changes every time the commander fires.
When being commander, you are sometimes randomly unable to release smoke rounds, like the button does not exist.
When being gunner, it happened to me once, that I out of nowhere instantly had the amount of ammo of the commander .50 cal instead of the usual amount of ammo of the coax gun.
When someone is already in the tank and you step in, you can't change places. The other player has to step out, then you have to step in - and then you can change places while being inside the tank. Same, just the other way round for the other player - of course.