My Elna didn't seem fussy about threads at all until I put one particular spool of black Coats & Clark on it. That thread wasn't "even" all the way through. It had thick & thin spots which drove the automatic tension crazy. I have since had 2 other spools of C&C machine quilting thread give me problems. Those 2 I was able to salvage by running several lines of Sewer's Aid down the spools and letting it soak in for a few minutes before I started quilting each day. The spool that sent my baby to the doctor got tossed! I also had a spool of variegated C&C that had the thick/thin problem but I managed to struggle through that one. I didn't know about Sewer's Aid back then.