Good news! The culprit was the stitch width (red) lever. It moved like it was working, but it never adjusted the width, well, not 100%. So yesterday I oiled a little deeper and when I set it for BL, swung the red lever to 5, and manually moved the paddle as I hand-walked the wheel. Click. Something gave and slipped back into place and now it runs beautifully. Full range on the width. Patience young grasshopper
