I honestly think the screw loosening issues are more prevalent in modern guns, S&Ws. As it sure seems it's all the newer ones that people are asking this question about.

NONE of my vintage revolvers have ever had the screws loosen up during shooting. They aren't gorilla tightened either. In fact, on my more valuable guns, I put less torque on the screws as to not bugger them or even risk it. They stay tight and still don't back out.

So while screws loosening can be from not properly tightening them, I believe newer production techniques and materials play a factor in this issue too.