When I try to create an motion study animation of a "large model assembly" (created by other "large model assemblies") during the rebuild my system stops (sometimes it crashes) ???  I have no issue when I do each assembly separately.  Also after the crash the assemblies are mismated, mates are frozen (like trying to change angles or distance causes errors), parts are missing, not sure what I am doing wrong.  The assembly is 200Mb.