Hey so I think I've run into one of max's lovely quirks. Happily modelling and one object seems to not smooth as expected. I think the last thing I did on it was a slice modifier. There are no double verts. I've tried exporting it and reimporting it. Basically everything gets tighter the more iterations are applied. Almost as if no smoothing was on (it isn't).
Here's the mesh.
Two iterations of turbosmooth
Result after reimporting
Any ideas? I'm probably just being stupid and missing something. Thanks for any help in advance.