All single action gripframe screws loosen up, it started with Colt, and apparently clones have to follow suit.
Ruger uses, or used to use Nylock screrws to help keep them tight, and they do wotk very well, for awhile. Some shooters use Locktite, purple or blue (DON'T use Locktite red, you'll need a torch to loosen them up again)
I check the screws before and after each session, and also if I feel the action "rocking" in the gripframe.