It must be the screw that my Jamone 6500 was missing. From the time I bought my machine, I couldn't get the feed dogs to come up high enough to feed fabric in evenly which affected the length and eveness of the stitches. Eventually another Janome dealer discovered that my machine was missing the necessary screw and it wasn't in the bottom of the machine so may have never been inserted in the first place. One small screw can definately be a problem.