Does any one know of a cause for an assembly to move past the limit mates?  I have an assembly with a swing part that is constrained with a limit mate.  This was working well, but recently the swinging arm will pop past the limits.  When you pull the arm thru its motion, the arm will pause for a second at the limit, then pop past.

This has happened to me on several assemblies in the past.  Does anyone have any insight into what causes these mate to break down like this.