In regards to adapter plates, why are you using an aftermarket one? Does the MOS not coming with what is needed?
Some people have complained the Glock parts are not the best design. Thread engagement is not the best seems to be a common complaint.
I have seen a lot of complaints about the plates warping or breaking. From some of the images I have seen it looks like installer error on some but not all.
After having a slide done by Agency Arms I think that is the way to go. I just bought a new Gen5 and once I put a few more rounds through it to make sure it is good to go I am going to send that slide out to them.