I believe this is a bug with the game and not with the script. I also think we can't do something to fix or prevent this from happening as it's not detectable.
NRG-500 (CarJacking Bug)
Locked
Unfortunately, It's a samp bug, Not only with bikes, But can also happen with cars, And player will be unfrozen when the driver leaves the vehicle.
Moved to Known issues
Moved to Known issues