I think we have a screw loose

Yep... one of the grip screws.

The lower left grip screw I'm sure is sitting somewhere at Stonewall in lane 4.  :-(I discovered it as I was cleaning the gun from a trip to the range. I called up Sig but they said it sometimes happens and that it's not a warrantee issue.Thankfully one of the shops around here (the one I got the X5 from) is one of the leading suppliers of Sig parts and accessories: Top Gun Supply. (I've got to say though, they keep the strangest hours)I needed one screw. I walked in and bought 4 just to offset the gas I burnt getting there.The screws come with a dab of thread-lock on them. Some red stuff. I've seen that on some screws from BMW -- they call it some variety of "micro encapsulated thread lock."I don't buy it. I'm sure the screw that fell out had some on it. I verified that all it's brothers had some on.I'm glad I checked them all. The other one on the left was somewhat loose too. The ones on the right were tight -- up until I took them out.I reassembled the lot with some good Loctite. I trust that stuff. The stick form of it is pure genius!I'm on the same stick for the past couple years now. I use it on the bike all the time. It's a lot less messy than the liquid version.When I talked to Sig they said to use red Loctite. Other than the stuff that comes on the screw which happens to be red, I don't he knew what he was talking about. The red is "permanent" and requires application of heat to break loose. From Henkel's tech data sheet I don't think it would like the "apply localized heat to approximately 250 °C. Disassemble while hot." it would take to take it apart.In any case, all's well that ends well.