We have several Singer slant shank machines. From the 401a to the 500s to a 4622a and T&S 778 and so far we don't seem have the troubles described here.
I've had to adjust the thread clearances around the hook like CD did but still no troubles like that. I live in IL where it's dry in the winter and sticky humid in the summer. Use different threads from different brands and the only problems were minor tension problems.
Am I doing something wrong?
Just curious cos I always wonder when I have the same machines others do and don't have the same troubles they do.
Joe