I had a very simple model, shown below.

The model has a pressure load over the blades and a 1 rad/s centrifugal load referenced at the shaft opening in the hub. The inner surface of the opening in the hub has a "fixed" BC applied to it.

The model runs fine with the pressure load, but once I add in the centrifugal load the model fails to run and I get a maxtrix singularity error. I'm baffled by this because I cannot see where there could be rigid body motion. Has anyone run into this and found a solution? I've scoped out the mesh and cannot see any location where there is a lack of a connection between elements. Is there a way for SW Simulation to find and animate rigid body modes?