Yeah, sounds like your tension is off. Upper tension too tight. That is probably because the monofilament is not the same thickness as the bobbin thread and it has less give than regular thread. I have used it in the past but only on straight stitching (in the ditch).
I got a bad roll once that broke every few inches and decided that I might as well stand by my quilting (however mediocre) and use thread that screams - HEY I QUILTED this!!