Sometimes the issue with the stitch width selector is at the needlebar side of things. At the top of the needlebar with the "door" open, if you push it to the right, it should move about 1/4" to the right, then move back when you release it. If this is gummed up, like the 401A I worked on, it will cause issues at the other end as well. TriFlow is your best friend as usual.