Question on closed four bar link structure.

[KaixinZhan]

Hi everyone.

I have a robot which contains several closed link structures. I set a mjcf file which has a correct dynamic results in Mujoco. However, if I directly import this mjcf into the Isaac Sim, the closed loops vanish. Is there a way to automatically get closed loops in IsaacSim, or must I do it manually according to the documentation? Thanks a lot.