So the main reason why it slides is because this implementation of the friction is reactive, meaning it react to velocity and if there is no velocity there won’t be any friction. The side effect of this is that object will start moving under influence of gravity and only after friction will react. This is why it slides.
There are two ways I know of to fix this. One is to add a breakable physics constraint when vehicle stops and it will keep it from sliding. The other is to use @0lento’s idea where a fix can be added to correct specifically for force of gravity. I haven’t tried neither of them on the actual tank model and just on some primitives. I’ll see if I can address this while rewriting friction code, which I’m busy with right now.
So short answer is that this issue will be addressed at some point.