Regarding the hard primer issue.
If it only happens in D/A mode it is neither the spring, nor the grip screw. If it happens in both S/A & D/A mode its probably the spring. If the grip screw is tightened too much, or is too long, then you should not be able to use S/A mode as the tip of the screw blocks the bottom of the hammer from rotating far enough for the hammer notch to be engaging the sear.
There are 2 lengths of screw for the small frames, so check that as well. I swapped to a Hogue grip & had to add 2 small washers because the grip screw supplied was too long. I couldn't go back to the original either as the Hogue had a much smaller head.
Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”?
Elderly Hunter: “That's dashed unsporting. Probably Belgium.”