Crash inside SceneKit [SCNPhysicsField _removeOwner]

I'm seeing a decent number of crash reports from our app where SceneKit is crashing internally relating to SCNPhysicsField. The stack looks like:

objc_msgSend
-[SCNPhysicsField _removeOwner]
-[SCNNode dealloc]
AutoreleasePoolPage::releaseUntil(objc_object**)
-[UIApplication _run]
UIApplicationMain
main
start

It must be that I am removing a node that has a physics field on it and it randomly crashes.

Probably threading related? Anyone know if there is a workaround, maybe setting physicsField to nil first before trying to remove the node?

Thanks