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.