Before your AddRelativeRotation node put a PrintString node and output some message. If it stops outputting when your wheels stop rotating, you know the node is not reached and the actor is not ticking anymore. You can also use the debug tools described in here to observe the values, maybe something sets RotateSpeed to zero.
Output the absolute y-Rotation of the wheels every tick (Print String). Do they stop at a certain rotation? It would be suspicious if they stop at exactly 180° or something like that.
If you did that we have more information and can work towards the solution
It’s a pity that this bug still exists, I had it before 2 years and it still annoys me.