Unusual physics in 4.7.2

I had my game working fine in 4.6 and updated to 4.7.2 but my main vechicle’s physics are messed up (I’ll come to what happens soon). Why it’s confusing is because it’s ONLY the spawned player pawn that is messed up. I made my blueprint so that with an editable value (defaulting to 0) you can place the BP in the level and it will move by itself. This is the exact same blueprint. And THAT placed, non-possessed BP works fine.

But my possessed pawn, the wheels no longer spins, it moves by itself in the air and I can’t for the life of me work out why it’s doing anyting like this. If I delete the node in the BP that activates the throttle, it still moves around… It’s very bizarre

Just to confirm some things I have ruled out:

It appears to happen to any spawned instance, not ones I have placed in the level.
So I moved everything out of the construction script (because I’ve had issues there before) - no change
If I disable all the initialisations (materials etc) - no change
If I disable all the event-tick events - no change.

And to reiterate, the placed BPs, when these are turned off, sit there still. The spawned one acts as if it’s collision mesh on the wheels is broken.

It’s AS IF something weird is going on with the collisions, it’s moving around like if it’s trying to resolve the physics, but ONLY on the spawned one