Sorry for the delayed response.
I have been studying your model and I see that there seem to be some issues with the Geometry.
You can use the 'Check Geometry' option by right-clicking on the component in the Structure tree or you can also use the 'Repair' tab tools to cross-check your geometry.
These errors in the geometry could have caused the issue.
I deleted the solids as highlighted in the below image and recreated them and then I also recreated the selection sets NS_N1 and NS_N2.
This seems to have resolved the issue.