Hi Gunter, so the other thing is the fillet will get extended because a spot like this is not a place where a fillet can end:



The fillet wants to intersect with a kind of "capping face" and there is not any such face at that spot.

So instead of opening up a hole in the object there, it will continue on until it finds a suitable face for the fillet to be intersected with like this one shown in yellow here:



- Michael