It’s easy to reproduce, just duplicate one of the terrain demonstration areas (ice/nature) and apply a new material representing the mud with FGear Physical Material (Friction 0.1 / Roughness 3.0) and remove the PhysMaterial in the GreyGrid Material Instance. You will notice that after leaving the area the vehicle will be “weaker”, unable to reach enough revs to advance the gears. (I can send you the modified example if you prefer). I belive it must be something simple, like because the default physics material doesn’t have the same values as the Fgear physics material, the plugin ends up keeping the old values in the calculations.
Also when crossing the mud area, you may notice that it is possible to turn the vehicle easily at the same speed as if going forward.
I also couldn’t reproduce the brakes problem in the Fgear example project, it must be something related to my project, I need to investigate further.
The event for the stall would be something simple, like the “On Brake State Changed” that is already present in the plugin but without the need to inform about the status change.