I've not heard of any problems with Group industries guns including the one I own. Many issues with the vector guns but a lot of them were sent back for refurbishment while vector was still in business and repaired. Likely an NIB Vector would suffer many of the issues you state (fairly common discussion in the early 2000's) and not have been sent back for repairs. From what I recall most issues were resolved on the first trip back, but some did make two trips. Vector got pretty good at fixing them out of necessity.
Hopefully your gun gets fixed this time! The good news is if you can wait it out 3 years maybe you'll be even or ahead as prices escalate.
Gunsmiths are a lot like contractors, they have steady clients that take precedence over a new guy and try to "fit" other work in when possible. That's just the nature of business, but admittedly like contractors there are also a lot of lazy gunsmiths.
Guys in general have "issues" getting MG's to work so a lot of commentary is not worth much if you are trying to solve a problem. I find 75% to be operator error for a multitude of reasons when guns don't work. They broke them, lost parts, didn't clean them, etc. If MG's were as available and cheap as golf clubs imagine how many you would see hurled out on the range!