The palm indent for the cutaway surface might be made simpler, with fewer nodes that cause fewer control points in the surface, indicated by all the isocurve indicator lines. That surface might be rebuilt. If it can, the result would be smoother, with possibly fewer filleting problems. If a fillet is meant to run across a whole mess of isocurves or segmented splits, it’s a sign that rough sailing might be ahead. If you are using a Boolean object to remove that, perhaps that could be rebuilt and simplified before it is subtracted.
Sometimes it helps to do solid merge all surfaces. I am not sure that its the case, but sometimes not filleting adjoining surfaces at the same time causes problems.
Some other things that will cause filleting problems:
- Not filleting edges at the same time, which also might be the issue
- Too large a fillet
- Inappropriate fillet type
- Filleting a surfaces that already have have splits, segments, and split edges–especially if an entire width/length of a surface may be eaten by the fillet
- Not filleting the adjoining surfaces
Generally, I keep step-wise versions, in layers, in files, when making deceivingly complicated things. Solid bodied guitars can be tricky to model.
Ain’t no curves on a BMW like that. : )