some quilters have waxed their machine!!
sometimes it's the batting, sometimes the fabric.
I've done it with feed dogs down and up. actually took a class and we left them up. but I've encountered problems off and on. i don't change my tention at all, nor stitch length. you shouldn't have to do that. the movement of the quilt determines the length of stitch.
try holding the quilt better and quilting in smaller areas. slower but may work better.
good luck.