I have developed a mannekin to use to test spaces for a project.  This is Michael:

Michael is fine as an SLDASM file all on his own,  all his jonts are mobile.  But when I tried to sit him on a floor in another SLDASM he froze solid.  Worst case of Rigor Mortis I ever saw. 

How do I free him up so I can sit him on the mattress?