There is a little grub screw on the opposite side to your clamp screw, this tends to vibrate loose, if it has worked itself out a bit then the other clamp screw can push the blade into the hole causing it to bend. Check if it has come out a bit (I think it what is used to adjust the blade to vertical) if it has then screw it in a bit , once it is clamping without bending the blade then you will need to check the blade is vertical, and adjust as necessary. Hope this helps Marg
Keith.