Perhaps it came loose itself with use . I tightened it and got back to work . When I switched to my straight stitch machine , again I found the foot had been unscrewed and was loose . While I do occasionally need to switch feet on this machine , I had done no sewing the day before that would have forced me to unscrew the foot to switch it out .

Question: What is the cause of my foot problem ?
Answer: It 's too old .None of the above choices .It 's not comfortable .It 's too tight .