If you are still having this problem, in the optimization tab increase the sleep linear and angular threshold speed to like 1 or 2. By default it is set to 0. Fgear vehicles at rest state never have a linear velocity of 0 due to vibrations in the simulation. Increasing the number will give higher sensitivity for sleep. In addition uncheck “spatially” loaded in the vehicle. So once the vehicle goes to sleep, it will never be unloaded even if the world around it gets unloaded. You don’t even did to change physics simulation settings.