Hello, thank you again for pointing this out. The way to fix this would be to suppress the MultiZone Mesh method and allow the geometry to be meshed using tetrahedral elements. I tried using a global element size of 3 mm and 2 mm and both were able to generate valid meshes.
I also tried inserting a Convergence object in Equivalent Stress. It did not work and the error message indicated that it was because certain objects were scoped to nodes/elements/element faces. This happens because we have a Named Selection in our model that is scoped to the mesh. When you use Convergence object, the geometry is remeshed and hence the Named Selection needs to be regenerated, but Mechanical is not able to do that. If you suppress the Named Selection and the Equivalent Stress scoped to that Equivalent Stress, you should be able to use the Convergence object.
However, when I tried using the Convergence object for Equivalent Stress of the Body (Type: Maximum, Allowable Change: 5%), I was not able to achieve convergence. This is probably due to a stress singularity occurring at the corner where the Max equivalent stress occurs. To understand more about Adaptive Convergence and Stress singularity, please check out this video:
Hope this helps! Thank you again for bringing the meshing issue to our notice.