We’ve just encountered this issue as well in 4.15. Is there any idea when it is going to be resolved? Our entire project has been stalled due to this issue. This issue also occurs if another skeletal mesh is attached to the vehicle and is then possessed by a custom player controller.
Setting the animation mode to use AnimBP in custom player controller and pointing to the relevant AnimBP causes a second instance of AnimBP to spawn which faces the same problem.
Also, vehicle AnimBP has problems getting controlled pawn reference.
We have a partial workaround where we can manipulate some bones on the vehicle by driving their transforms through variables in the vehicle blueprint. I guess it can be extended to the bones controlled by the wheelhandler. But that is not a feasible solution, as everything calculated by the wheeled handler would need to be done in vehicle blueprint causing it’s size to inflate to a disproportionate size. And that is as good as rewriting the wheeled handler all together.
We need a workaround really fast, so please let us know how we can help.