So in the middle of piecing a quilt, my top thread became a straight line with bobbin thread loops on top. So either my top tension suddenly became too tight, or my bobbin tension became too loose. I lowered the top tension to the lowest setting, and it made only a slight difference. Just for testing sake, I adjusted it incrementally to the highest setting and it got tighter and puckered up the fabric even more so it appears the tension dial is working.
I re-threaded the machine and changed the needle. It would stitch fine for a few inches and then back to the top thread being way too tight. I removed the bobbin case and cleaned out all the lint. I flossed the upper tension discs. Everything was fine for a few blocks and now the same problem again!
I've had this machine for nearly a year and until now have never had a problem. It did not happen until some time after I started using a new piecing presser foot (the little foot by Lynn Graves). Could the foot be causing the issue? Is it time for servicing the machine? Is something broken? What should I do?