Uncommon quickfix is actually to disembark, then unequip from hands binoculars and get back as gunner into the vehicle.
I've selected major severity, because :
- Each time a teammate boards a vehicle with me as gunner. I need multiples minutes to explain him all bugs that might happen and all missing features.
- I kill all the time people who seem having this bug and who don't shoot me back or who can't aim.