Actually the one arc on the lower inside is ok - it is an arc in the upper-left corner that is not quite tangent to the line it is next to, it comes within 1.5 degrees of being tangent.

Things that are very close to being tangent but just a small amount off tends to be problematic for the filleter, it will see it as a sharp corner and try to construct a fillet corner piece there which will be microscopic and tend to gunk things up.

So another tune up is to get those arcs and lines to be trued up instead of slightly off.

- Michael