TNA is great. Only ever had two issues (if you can even call them that).
First, a fake supressor I ordered had been scuffed during transport I assume. Contacted them and they were quick to reply and very apologetic. Told me to send it back to them and they would replace it at no cost to me. They must have shipped it when they got my email judging by how fast it arrived. If I remember correctly it was all in the same week.
Second, I ordered a handguard but they didn't have the length (17") I was looking for, so I went for a 15" instead. And lo and behold, I actually like it better.
So yeah, hardly issues at all. They're top notch.