Please help,

I just bought a Berretta U22 NEOS and it shoots great.... One day I watched my target hits drift to the right.... couldnt figure it out at first, then before I knew it the sight adjustment screw was on the ground.... I put it back it and it backed out again. I was thinking of putting some locktite in it, but I'm afriad then I cant adjust it.... please help!

Thanks,
Shawn