Problem when creating solid difference for waffle

Hi all,

I have run into a problem when creating a waffle.  Everything seems to work fine except for the solid difference.  It cuts notches in each of the ribs, however it does not cut the same notches in each rib like it should.  I am trying to cut this object with a laser cutter and then assemble to create the object.  I am pretty new to grasshopper so any advice is welcome.