I noticed that you have a solid body meshed with solid elements. Thin parts like this should not be meshed like this. Open the Geometry in SpaceClaim and on the Prepare tab, click on the Midsurface button, then select the top face and then the bottom face of the thin part and click the check mark. It will automatically create a surface in the center of the thickness of the solid body, and remove the solid body from the analysis.

Close SpaceClaim and reassign the Fixed support to the circular edge now that the face is gone and rerun the analysis.