Any machine can have tension problems. It is a matter of understanding how a tension works. I'm thinking if you look in the sticky notes you may find resources for adjusting the tension. Or go in the upper right hand corner of this page and search tension adjustment. It isn't always that knob that is the problem with a tension. The Singer machines made before 1970 are pretty much ok. The Japanese machines with out plastic are pretty much ok. But anything can happen once they are in someone's hands. I have serviced a lot of machines that don't work. They are mostly user errors. I am mainly on another board these days as are a lot of knowledgeable people.