Not saying this is an elegant way of solving this problem but it is an easy fix.
Cut small pieces 1/4"x3/4" supple leather, position it over the arrow groove and depress your shafts into the groove forcing it to the bottom of the groove. The leather will, of course, wrap tightly around the shaft making it perfectly snug.
They hold really well but the leather does come out when you remove the shaft (sometimes). Good for stand hunting when you only remove one arrow. You can save the leather if conscience of it but if stumping or other, you likely lose your leather strip in haste.
I have gone whole seasons w/o losing my leather gripper strips
Good luck -
Kris