Three factorizations in a row failed. Check the model. It is possible that the model contains the kinematic coupling definition set up in a way that a degree of freedom has neither mass nor stiffness.

I'm getting this error in the modal analysis

If I just model a homogeneous beam, the job runs OK, but when i try to define a two-layered beam, and use connectors to joint the two part (like in this example https://www.youtube.com/watch?v=I5Uq3USDqd4) it gives me the above error...

It is cleary related to the connection, but i don't find any information on how to solve it....

Any suggestions?