When I begin to sew, a few stitches are taken and then it freezes up and in checking, the thread under the plate is bunched and looped across the bobbin. I cannot determine whether I have inserted the bobbin incorrectly but it has happened for the past two weeks and am unable to correct the problem.

It is a Singer machine model 4423 heavy duty and it sewed fine and I am using thread to sew upholstery fabric into cushion covers for porch furniture. I sewed one so far and didn't have any problem. I had a very old machine which was 50 years old so I am a novice with this one so I need very basic directions. I made sure that the machine is threaded properly but what else could be causing all of the thread bunching up around and across the bobbin that it won't let me sew. After taking two or three stitches, it stops sewing.

Can you explain what I should check again, please.

Thank you. Vicki