I commonly experience a pretty vital bug about 1-4 times per play session when using any vehicle. It happens consistently during any questing or battlgrounds like Strand of the Ancients as well as Wintergrasp where I have to use a vehicle.
The bug seems to be interface related where it will glitch out completely or have the vehicle HUD repeatedly loading/bouncing into view of screen until I /Reload.
However the 2nd most prominent bug that happens even when the HUD does not visually glitch out is where I enter a vehicle and cannot in any way use Action 1 on the action bar. Even if i press the KB button or use a mouse to click the ability I cannot use it, I even tried re-keybinding it and it still would not work. The only fix I have found is to exit the game and restart the WoW client entirely.
Multiple other players have mentioned this as a common bug for them as well.