Hi Chris, I've still been looking at your model to try and figure out what's going wrong with the fillet. I haven't got it figured out yet but it seems to be failing in the phase of building fillet surfaces, I'll be looking at it some more to see if I can figure out what is going wrong. So far it looks like some kind of bug in the filleting mechanism though and not really any problem with your model.

If you need it finished right now doing some alternate construction method in those areas where it failed like as Burr mentioned deleting the side walls and putting in a loft there sounds like it will be enough of a different structure to avoid this particular bug.

- Michael