If I am reading your description of your problem with the bolt stop correctly, I have a couple ideas that might be of help. I checked one Springfield M1A and two Armscorp M14s I have built myself.
On my rifles the bolt stop does not make contact with the left cartridge when released, even when I press the bottom of the bolt stop upward from outside the receiver. The bolt stop rests on the far left side of the firing pin retracting bridge, there is a small ledge cut into it for this purpose. I have noticed some bolt stops are larger in their dimensions than others especially in the area that makes contact with the bolt and extending forward. This could be the cause of your problem and your grinding them down seems just what is needed to fix the problem.
You also indicate the bolt when moving forward presses down on the bolt stop. On my rifles the bolt does not make contact with stop once the bolt is released. When I was fitting the bolts to my Armscorp receivers, I had problems with the receivers not being within specification in a few areas. One of the areas out of spec that affected the bolt was the receiver bridge bolt support surface. This is the curved bearing surface that supports the upper back ridge of the bolt, it is right behind the cartridge clip guide.
On the Armscorp receivers, this area was not beveled enough and caused the bolt to stick when it was retracted and the bolt was hitting the bolt stop until I enlarged this area with a Dremel tool. I did not have the problem with feeding like you have, but you can still check this. Check this area to see if it is causing the bolt to move downward and hit your bolt stop. If this is happening this area needs to be enlarged so the bolt does not stick or move down. I hope this is of some help to you.
