I'm trying to run an FEA on a multi-bodied part in an assembly.  The assembly is just mock up parts just for simplicity.  I've added all the contact sets, loads and fixtures and run the analysis.  It finishes without any errors and the results appear to be accurate.  The results show it can't handle the stresses so I needed to increase the diameter on all the pins (actual pins, not the simulation feature) in the part.  Once I do this, the study will no long run, telling me that assembly isn't fully constrained.  After applying the "Use soft spring to stabilize model" it appears that the contact sets are no longer working and the parts are floating.  There isn't any rebuild errors, the parts don't interfere, and as far as I can tell, there is nothing wrong with the model. 

Why have the contact sets stopped working after modifying the dimensions of the surfaces they are applied to?