could the bow be torquing in your hand?
my shelves i like to build so that the arrow only has about a 1/4" of contact both on the shelf and the strike plate, in other words, both the shelf and the strike plate are convex shapes with the apex of both surface being at the same point on the arrow. and as a side note, its best to have this contact point at the deepest part of the grip, and not forward of it- as so many bows are- this also relates to thetorquing issue.