There's a command: /bounce which makes your vehicle jump, so you can just bind your wanted gamepad key to that command and then everything should be fine.
I tried this way but its still not working on my PS4 Controller.
Did u changed the command for bounce?
i cant bind or change my key/joy button for jumping
for example i write in Console unbind lshift then i still can jump with lshift
and nothing change when i try : bind g bounce