Another boolean modifier problem Blender 2.78. i have a model that as best i can tell has all of these for every object on every layer:


all normals correct
no doubles
no internal faces
no loose geometry
fully manifold


the three cutouts for objects are to be applied using boolean ops to carve away affected geometry; lift guide, glue plugs, and lift nuts. the first two apply properly. when the boolean op for lift nuts is added, the window clip disappears.

i've browsed page after page of boolean op problems here and elsewhere and gone over my model intently. i don't think i've missed something so then i'm left considering that i'm naive to some aspect of this.
From my experience it seams, that when using boolean you should always make ends of hole cutting mesh, stick out of the mesh, that is being cut. So in this instance you have to go to edit mod and raise up top vertices of bolts, above surface of window clip and lower bottom vertices of bolts below surface of window clip. This will solve the problem.
p.s.
By bolts I mean cutouts, lift nuts and cutouts, glue plugs