The engine has a feature to replace a dead driver after a short while.
However if the cargo is not in the same group, this only works once.
Workaround: Reapply addVehicle - despite already the assignedVehicle, this does the trick.
Demo video: https://youtu.be/7Y8aAdAxmU4
VehicleRole for the just killed driver returns empty . So it should not block the position.
Reveal doesnt help either.
(leader cargoGroup) reveal [(driver truck),4]
cargoGroup reveal [(driver truck),4]
Where driver is dead .p3d body: 2522a12f940# 17: b_soldier_01.p3d
cargoGroup is passengers group name.
No visible change - they're just sitting.