I'm doing a simulation of a multibody system. At first,I build the model in solidwirks then import to simmechanics. The whole body is connected by several universal joints and cylindrical joints. To the each joint, I calculate the stiffness.But that will cause the singular motion of some joints and it's random. Let's say,When I decrease the stiffness by about 100 times,the joints seems connected the body,eventually the whole body still separate into several parts even singular motion. I wonder if the decreased k let the joints work,then I increased the k,the bodies should connected more tightly,buy it's not.