I've found a temporary fix:
mp.events.add('playerEnterVehicle', (vehicle, seat) => {
vehicle.invincibility = false;
})
From what I've tested it fixes the problem.
EDIT: Or so I though, but i think it was something else I've done. If I find anything related to JS I'll update.
EDIT 2: Code is now correct.
EDIT 3: Sorry for another edit. This seems kinda random right now. I've managed to make it work with this event twice, but now it just kinda stopped working. So far I've tried:
vehicle.setInvincible(false);
vehicle.invincibility = false;
vehicle.invincibility(false);
And using natives. Nothing seems to work right now.