Hi Oliver,

> Everything worked fine except with one that
> partially failed (-> screenshot).
> Any ideas why ?

It's because of the "seam edge" in the base surface shown with the arrows here:



That's probably the biggest problem with the fillets in MoI currently, they will not behave properly when they have to cross over a "seam edge" that is close to but not touching the original edges that are being filleted.

So to avoid running into that problem currently you would have wanted to rotate your base shape a little bit so that the seam edge was not so close to the piece being cut out.

I can probably patch that model up for you though, by copying and rotating in one of the pieces that did fillet ok and then trimming that into place, if you'd like to post the 3DM model file or send it to me at moi@moi3d.com, I can try to repair it for you.

- Michael