I have a Brother 1034D--sew on it daily. Have had it about a year and a half or so. Never any problems. So recently, while serging, the right needle thread keeps breaking. Only the right...never the left. I've changed needles twice (same needles I always use), put new cones in, rethreaded numerous times, changed the tension (which I've been using the same tension since I bought it--not sure why that would be an issue all of a sudden), cleaned and oiled...I'm not serging anything different than I always do--I'm making diapers. I'm stumped. Can anyone think of any other reason why this would happen?