You must not read many posts.
NEA has had quite a few negative threads started on here with people having issues with their products. Most of the barrel issues are simply of them being slightly overgassed though. I can only recall one or two threads about loose extensions.
The good thing about NEA though is that they are very quick to stand behind their product and replace whatever the person is having problems with. These issues seem to be getting less frequent as well so it sounds like they have upped the R&D and QC.
I'm sure they are setting the gas port size slightly on the large side to ensure the rifle will function with any ammo it's fed but that also translates into more harsh recoil when using hotter loads. It's a tough balancing act as they must size it so it cycles everything or customers will complain the rifle is unreliable but at the same time must try to size it small enough to have the rifle run smoothly.
The 7.5 inch barrel rifles are tough to balance so they run reliably and smoothly, it can be done but it takes a little more work as there is a very short and intense pressure pulse to deal with.
What buffer, carrier, and spring are you using?
You need to shoot it as Suputin said. Don't let the internet scare you, we only hear about the bad experiences since the guys that don't have problems are busy shooting their rifles.
NEA sells a lot of rifles and parts and I'm sure the failure rate is small if you were to look at the failures per units sold ratio instead of just reading about the problems people on sites like this have.