Blender - Subsurface Modifier causing extreme pinching in L-shaped corner I am working on creating an ISO enter keycap in Blender. Everything was going fine, until at the end where I applied a Subsurface modifier. Once I put the modifier on the mesh, it causes extreme pinching in the L-shaped corner of the mesh, where it looks like the mesh is overlapping each other and looks almost like a surf wave. I think it might be caused by the interior corner bevel but I'm not sure, does anyone know why this is happening?
Below are images of the model. Note: I have turned on Cavity in the Viewport Shading menu in order to make the issue more visible.
Top:

Bottom:

The model is also curved as you gave see from the front profile:

This is the mesh without a Subsurface modifier:

This is the mesh with a Subsurface modifier:

A closer look with a Subsurface modifier:

This is the mesh topology with the Subsurface modifier applied:

A closer look at the topology with the Subsurface modifier enabled:
You have ngons in your mesh.

As I only now see that Christopher explains in his comment above, your pinching is a consequence of using Subdivision Surfaces with non-quad based topology. SubDs only want quads.