Usually, factory refurbished goods haven't had any problems at all. Sometimes they are just store demos. The units are returned to the factory where the are cleaned, adjusted, and checked for performance. If there is a technical problem, they are fixed and are inspected using the same criteria as brand new.

In 1968 (there I go revealing my age) I took a tour of the Westinghouse picture tube factory near Elmira New York. The guide who was a production manager mentioned in the tour that if a tube didn't pass final inspection, it was cut open and reworked. I asked him how you could tell afterwards which were the "good ones" and which were the reworked ones. That was the wrong question to ask. He got rather irate telling me that when they left the factory they were all the same. Maybe I hit a nerve. Maybe he was having problems and didn't want an outsider sticking a pin in it. I don't think it was very much longer before they closed up shop. (I have a hunch it was eventually bought out by Sony but I'm not sure. Trinitron tubes are a different animal.)