Ok, I understand the self intesection problem and the meshing trouble.
But here's an other example :



For an unknow reason, filleting the last bottom edge of this model make some surface dissapear ... however, the object type panel is still showing this as a solid :S

Of course here I have a good visual feedback and I can fix it, but sometimes this kind of missing surfaces appends in some tiny fillet area, and I only see it after the mesh export (flipped normals) ...