I just noticed on my P99 that the roll pin at the top of the trigger blade (right up against the frame) was on its way out on my gun. I drove it back in easy enough but I thought I'd let you know to check yours.
Keep a close watch on that roll pin hole !! That is does not enlarge or oval out. Sig has had some problems in this area with some of their larger caliber guns. ( A roll pin that holds the trigger group in place )
I would go as far as odering another roll pin..........in case the one you have has lost some of its expansion properties.
This would bother me........ unless your gun has some higher round counts in the 50 K range or more.
Acually this one's the one that holds the trigger plate on. On the blown up photo from the P99 FAQ it doesn't even have a number. If the hole opens up a new pin wouldn't help, but it was a bit snug being pushed back in. I've only got about 2500 rounds though it so far too. I'm gonna keep my eye on it too, if it's worse, I'll send it to Walther under warranty.
I am surprised it came out on it's own accord. It took all I had to drive it out of my P99 AS due to the slide stop spring breakage. Took almost more effort to get it back in. No movement yet. Had a backup on hand due to the proprensity of rollpins to lose their tension qualities after removal...but no issues so far.
Heard those roll pins are pressed in..after the beating I gave it I have no doubt!