Hello ianyylai, maybe try to use MPC formulation in this connection and check in Contact Tool if the connection is closed. It should solve your problems. If you want you can also turn on Weak Springs just for a single solve and after solve you will be able to check on deformation contour plot where occurs the lack of required connection. Then change options for that connection solve again with weak springs and judge if its okay. If okay solve once again, but with Weak Springs turned OFF. Then do final check if its okay.