Where exactly do these "refurbished" guns come from?
Customer returns?
Almost certainly.
And do they tell you what the problem was with the gun before it was refurbished?
No.
A lot of people see the word "refurbished" and avoid it like the plague. I can't vouch for Uberti, but here's an example from the industry that I used to be in.
Back in the dot com boom, I worked for a big computer company. Sometimes things wouldn't work out with a computer and we'd take it back. We had a department that would process the returns, figure out what was wrong with them, toss out the bad parts, put the good parts in the bins, build "new" computers out of those parts, then resell them as refurbs. There was no way to say what was "wrong" with the computer because it was built of parts from many different computers - and many that were returned had no problems at all (we offered a 30 day, no questions asked guarantee).
Our return rate on new computers was somewhere around 2.5%, which was a little below the industry average. Our return rate on refurbs was about 0.25%. The difference? The refurbs were tested much more thoroughly than the new systems. I can't say for sure, but I suspect that we ultimately broke even or lost money because of the additional labor cost.
All of us who bought computers from the company bought refurbs because we knew that they were the biggest bang for the buck.
I have no idea what Uberti does to refurbish a returned firearm, though. I just thought that I'd offer my experience on the manufacturer's side.