There must be something wrong with the topology or some kind of settings I’m unaware of? I’ve tried merging by distance—there were no duplicates. Can someone help me understand what’s going on here?
This is the mesh.
This is with subsurf.
Ok, one more part to the issue. In the second to last image—that sharpened right hand edge—if I delete the faces and re-add them, it subdivides smoothly. If I do it all at once by bridging them as edge loops (which I suppose is the problem elsewhere) it looks as it does. Can someone help me understand why this is?