I had the same problem with my HQ Avante......to the point I finally insisted he come to my house to see what I was doing wrong. He IMMEDIATELY saw what was wrong........the back bars had been set too high. If the bar is too high, the fabric goes up and down with each stitch and "saws" at the thread. Make sure your fabric isn't sitting too high. My biggest problem with the repairman was he didn't put the machine on the table.....he just put fabric up to it like he was sewing on a domestic sewing machine and kept saying it was working. Good luck......keep insisting they help you. If you have to, take it in and SHOW them. I hate when they ask what the problem is and then get it all wrong when relaying the problem to the repairman.!!!!!!