I’ve never had any problems with my Model 12 that I got two years ago.
You say the sound from the computer degraded - that’s where I would start looking. Especially if it’s a Windows machine. I’ve worked with different Windows based computers since the late 80’s and I have yet to experience one that never behaves erratically.
If you have an Apple computer, then it sounds slightly more weird, but I’m guessing that if you only use the Model 12 with analog sources, there’s no problem. Drivers, updates, USB standards/cables, weird hardware incompatabilities and so on, are all reasons why I always eliminate the computer when something goes wrong in my setup.
But my Model 12? Never had a problem.