Gun Plumber,
Does your friend dry fire his P99?
I also had two strikers break. Earl thought it was due to dry firing. I stopped dry firing and the strikers stopped breaking. However, I am not certain that dry firing was the cause. Walther has strengthened the striker, and my third striker was one of the strengthened strikers. Moreover, I wrote Walther in Germany. Walther told me that the P99 was designed to meet the specifications of the German Police, one of which was 5,000 dry fires using snap caps, and that the P99 was one of two pistols to pass the tests. (I think the other is the USP Compact.) Given this, the 400 or so dry fires I did on each striker should not have caused the failure.
By the way, have you heard of any other barrel lug failures?