I tried varying the stitch setting, cranked it really high to get fairly normal length stitches.
I have a Janome Harmony.
Last night I tore it apart to see if there was a big ball of fuzz under the plate. No.
But, I did notice that the plate holding the feed dogs was wiggly. I tighted that, and now it seems to be fine.
I had never thought about the feed dogs having something which might need tightened. A new learning experience.