I have done very few Motion Studies in SW and I need advice on a problem I'm having with a current project.  I have created a fairly complicated assembly for a client and everything moves properly in the model.  The assembly itself consists of six sub-assemblies, several of which are in turn comprised of other sub-assemblies.  Counting the parts in the sub- and sub-sub assemblies, the top level assembly has about 700 parts.  There is a hinge-type motion that takes place between two of the largest sub-assemblies and this behaves properly in the Motion Study, despite the use of limit angle mates, which I've heard can be problematic in Motion Studies.  One of the small sub-assemblies is a group of five pneumatic toggle clamps and its these that I cant get to work the way they should in the Motion Study.  I use a coincident mate on the clamps' arms, so that dragging the arm of any clamp makes them all move.  A limit angle mate is used to constrain the motion of the arms.  Seemingly without any consistency, one of three problems occurs during the Motion Study.  Sometimes the clamps don't move at all.  At other times they go to the open position as they should, but then immediately snap shut.  (When this happens I can see a very light and short yellow line on either side of the Time Bar).  Finally, sometimes after I hit the Calculate button, the keys denoting the end of the clamps' motion turn red.  I've tried disabling all of the limit mates, but this doesn't seem to make any difference.  A Confidentiality Agreement prevents me from posting any files, so this description of the problem is about all I can offer.  Any ideas what I should try next?