Hi Wim, it seems to be having some difficulty generating the fillet surface in these areas here:



But I don't see any particular problem in the shapes themselves that should be problematic, so I think it's some kind of bug in the fillet processing.

Since the cuts are symmetrical and fillets are being generated on other areas (once I replaced them with some analytic planes using Construct > Planar), it should probably be possible to mirror one of the ok fillet pieces and then manually trim the fillet into place, I'll see if I can do that for you.

- Michael