Hi Randy, I'm not entirely sure but it may possibly just be a bug in the display mechanism and not in the actual surface data itself.

When I load your posted file, if I just directly export to a polygon format, the generated polygons do not leak out like you see in the display - in general the export mesher does a kind of more careful and thorough (and also slower) job of generating polygons and possibly some shortcut in the display mesher which is oriented towards speed is making an improper display mesh in this particular case.

Also the same file without any retrimming seems to check out ok in other programs as well, so that also leads me to think it's a display mesh bug and not an actual trim bug.

I think the display mesh bug has something to do with a very slightly wavy diagonal trim curve in the UV space of the surface.

I've looked at the UV curves themselves and they seem to be ok too, so that's some more indication that it seems to be a display bug.

- Michael