I removed that option in the most recent release. It was causing some issues for a few folks, so I've removed it for the time being.   That's actually backwards from what I usually hear. Not the exploding part...but that kerbals usually ragdoll when touching a leg or wheel. We are looking at the wheels and landing legs. Unfortunately it's looking like a unity upgrade will be needed. There were some fundamental changes to the way PhysX and Unity handle wheels, and the downside is