I had a gas block slide forward on a cheap build I did. My groupings got bigger and it started cycling weird. Once I pinned it properly, it fixed everything. Ever since then, I don't trust just set screws by themselves.
Ruger Max 9's had an issue with the slide stop spring slipping off allowing the slide stop to bounce locking the slide back randomly. I tried a few fixes and eventually sent it back. It hasn't done it since.
Back in the 90's I bought an Early Kel Tec P11. When I got it home the rear sight fell out when I took it out of the box. I lightly staked it and took it shooting. Then I had a lot of FTE's. I looked and the extractor had a radius. After I filed it square I realized that a shotgun had better patterns.
So I took the slide to work and compressed it several thousandths at a time until there was a slight resistance fit on the rails. I polished the rails to a glass smooth, airtight fit. Of course the barrel wouldn't go back in so I reamed the barrel opening and lapped the lugs to a slight resistance fit and polished as well. I also had to ream the firing pin channel as well. Since I was already "mutilating" it I took it to the belt sander for a Meltdown treatment. Afterward the slide got a baked on Moly/Teflon coating and decent springs. Now it's acceptably accurate for what it is. A DAO Micro isn't going to win any matches.