I know this is going to sound strange, it sure did when I was told to do it on a mould screw that would not stay tight . Take a few strands of 0000 steel wool and wrap around the lower half of the offending screw, it doesn't take much at all, just 1 or two strands, and screw it back in .
I'm not sure why it works, but the mould screw has not loosened scince doing it. It's cheap to try and not something that can't be undone .
Gary