The stock needs to come off the gun to answer this riddle. Could the tang be bent? Screws not tight? Does everything else work flawlessly? If not, other issues could be related to the tang. I tend to aggree with other posters in that the work looks very good, its odd to see good work combined with that much over sanding. My guess is the gun is not over sanded that much and that there is another issue, possibly small, that is causing the tang to be raised up so much. Just a educated guess though.
Steve