FDS Error 27 with Retuning/New Belt?

[Ianr757]

I recently purchased an FDS with (supposedly) improved tuning and a replaced belt. I keep getting error 27 issues with every game I put in though (cleaning games improves this issue slightly but still won't get me past a game's title screen at best and is only temporary). I have tried all six of my games with the same results. From what I can tell, this issue has to do with the FDS itself and not the disks. Did I get ripped off? What do you guys think?