【讨论】请教：下面的几个错误主要是什么原因造成的？？

traveller-CAD

1。   ***WARNING: SOLVER PROBLEM.  NUMERICAL SINGULARITY WHEN PROCESSING NODE 4  
             INSTANCE ZGD-1-2-1 D.O.F. 2 RATIO = 6.14922E+11
  
2。***WARNING: SOLVER PROBLEM.  ZERO PIVOT WHEN PROCESSING NODE 4 INSTANCE  
             ZGD-12-3-1 D.O.F. 2
   
  OVERCONSTRAINT CHECKS:  
  An overconstraint was detected at node 4 INSTANCE ZGD-12-3-1. There are multiple constraints  
  applied directly or chained constraints that are applied indirectly at this node.  
  The following is a list of nodes and chained constraints between these nodes  
  that most likely lead to the detected overconstraint.
overconstraint －－－－是什么意思？？

traveller-CAD

BC会有哪些方面的问题呢？？？
请讲详细点，谢谢！