Steps to reproduce:

1. Open attached project "825474.zip"
2. Open the RagdollShaker scene under Snowboarding/Scenes
3. Press play
4. Notice that as the character gets bounced around by the movement of the "box" he is in, he generally remains reasonable-looking - like a (limp and unconscious) human being.
5. Click the "Disable + Enable" GUI button in the top left. Do this several times, as the character gets bounced around.
- Notice that over successive disables and enables, the character becomes more and more mangled. Arms get bent and stuck at strange angles, bones (especially the spine) tends to get twisted at odd angles, the knees & ankles get folded in underneath the character in a strange way.

Reproduced with: 5.3.0f4, 5.3.7f1, 5.4.2p2, 5.5.0b11, 5.6.0a2