Set All Bodies Below Simulate Physics for "Pelvis" detaches Mesh from CollisionCapsule?

I’m trying to put my character into a a fullbody ragdoll, but if i do that on “Pelvis” it detaches my Mesh from the CollisionCapsule. I tried this with the standard ThirdPerson Template and with various versions from UE4.9.2 to UE4.11.0 Preview 4. All the same. I read somewhere that people modify the core engine to be able to set the Root to fully Simulate, but is there any good reason why UE is treating Physics this way? And specifically why does this happen for the Pelvis and not ie. Spine_01 then?