The first STLs were in bad shape, mine only fell off (free/unconstrained nut snare), and the top "clip" geometry had an overhang that was not really conducive to printing.
I simply remade the file (no errors), added a chamfer to the overhang, and added a little layer between the underside of the bed and the nut, so it holds tight to the underside of the Y carriage.
P.S. Warning! The Gcode attached is for the 12" Makerfarm i3v, so it may not fit your buildplate! Slit in Simplify3D, so it is fine and clean :)