Fillet, again and again :)

 From:  PaQ
2211.1 
Hi Michael,

If you have some time could you explain me why this kind of shape is so hard to fillet (yellow edge). Everything over 0.2 (circular) failed (and it's really tiny compared to the object scale).
Of course there are other option to create nice blending in this area, but I'm just wondering why is it failling (there are no edge crossing over, and surface to surface blending don't work any better)




Thanks a lot :)

EDITED: 3 Dec 2015 by PAQ