This is a very rare crash that I encountered in Vehicle Game and so far have not been able to reproduce, however checking the crash history it has been seen before in the wild.
This issue may be related to UE-40953 as the crash occurred when I quit the game with that issue happening. I have tried to get this crash again with the above issue, but as I said it is rare.
Have access to Vehicle Game
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-40956 in the post.