This is a common problem on all fender style bridges and has NOTHING to do with quality!!! I've seen it on Squires, and $5000 Fender custom shop guitars. And G&Ls. It's not a big deal. (Happened all the time with my 1960 Strat, until I figured out how to fix it. Is a $40,000 hunk of wood high-end enough?)
First rule: When you are adjusting these bridges, always make sure that your final turn of the set screw applies positive pressure (clock-wise rotation) to the set screw. That alone will fix 95% of the problems.
And if you don't want to buy an expensive tube of Loc-Tite for one toothpick use--try some of your wife's Sally Hansen Clear Nail Polish. OR, if she uses a lacquer-based hairspray, such as Final Net, you can spray a small amount on a cotton swap (Q-Tip) and wipe the top of the set screw. Presto! The bridge won't change until your next set up. And you fixed it CHEAP! (I like cheap!)
Yeah, little things like this can make us question our sanity at times, but they are afterall, imperfect, being made by humans.
Beautiful ASAT, jsup! Remember to smile when you play her!
Bill