Look on the Analog Forum below...there are many threads about broken TEAC/TASCAM decks.
Not sure what kid of expectation you have about buying used gear that has been out of production for many years...
...and then worrying about it's operational functionality and build quality???
I had one AKAI deck for 30 years (GX625)...never an issue, and the guy I sold it to is still using it.
I'm not saying there aren't TEAC/TASCAM decks still chugging away without issues, just keep in mind that both have been out of production for a very long time.