I think I may have stumbled upon part of why my workaround works, and maybe part of why this is happening. It looks like the On Hit Event is firing and being processed before the body actually makes contact.
I setup a quick debug scenario, where the bones will setup constraints that are placed on the bone that makes contact, and then attach to nothing (rooting the bone in place). What I saw was that the bones would make contact, but then snap back to some position away from the surface, seemingly before the physics body for the bone makes contact.
Here’s a video of the behavior:
Any ideas what I'm looking at here? I think this might be part of the root of these issues