Erik Kostson
Ansys Employee

There is something going on with the joint elements as per log - have a look and see if you can avoid them perhaps.
This message is often due to overconstraint.

So for this check: any region (edge/face) that is shared by joint and other boundary conditions.

If there is nothing obvious then the best thing is to:
removing the joints and reintroducing them one-by-one until the LAG MULT violation occurs is about the only way to be absolutely certain of the problematic connection. Newton-Raphson residuals might also indicate if there are any joints that are over constrained and causing force imbalance.

All the best