Hi Anthony, so your new piece has a different problem in it where it folds over itself in this area:



That could be due to a problem in sweep that has been solved in MoI v2 where sweep was sensitive to the control point spacing of the rails and could cause the sweep to kind of "bunch up" if control points had different kinds of spacing between them on the different rails.

There have been a lot of things improved in MoI since v1 actually - the current trial version is actually about 1 and a half years old now, v2 is almost ready to be released with a lot of improvements in it.

One other note - you have a lot of curves in your model on the same spots as edges, that can make it difficult to select edges so you probably want to hide those curves after you are done using them to get them out of the way. If you select a curve and then try to run fillet, it won't work, you need to select the actual solid's edges and not the original generator curves if that makes any sense.

There is also an alternate filleting mechanism that can sometimes help for filleting difficult cases - that's the surface/surface fillet which is activated if you run Fillet when 2 individual separated surfaces are selected. Sometimes doing fillets at that individual surface to surface level can be a way to fillet a model that is not behaving well with the edge-based filleter.

- Michael