Hi laurent - looks like the fillet engine had some difficulty trimming the fillet piece with the surrounding geometry.

When the fillet engine runs into trouble automatically processing some part of the fillet, it will usually spit out all the fillet surfaces that it was able to generate so far so that you can try to use those pieces to do something with them. Like in this case you can probably do a boolean difference using the fillet piece to get the end result that you want.

Are all those surface pieces joined to one another, or are they possibly separate surfaces that are just sitting next to one another and not joined?

Is your model at some very large or very small numeric scale in overall size?

Can you please post the 3DM model file along with your screenshot when you have a question about a particular situation like this? That then makes it possible to examine the actual structure of your model and to zoom in to it, look at it from different angles, try to repeat the problem, etc... none of which are easily possible by just looking at a screenshot alone.

- Michael