Well done not the easiest job. I myself recently encountered the problem of a terribly working machine, but unlike you, I quickly gave up and did not devote time to fixing this machine and bought a new one. Perhaps this was not quite the right decision depending on your work :)
But, to be honest, I have no regrets, because singer sewing machine troubleshooting every issue that I have. I think that both of our ideas had the right to life