Originally Posted by
Watson
IMO, your top tension is too strong in these pics and is pulling your bobbin thread up. This will also give you the extra bit seen on the corners.
I would re-thread the bobbin into the bobbin case and try again. If it continues, regardless of how you re-set the top tension, it is likely a bobbin tension thing and you may need to adjust the bobbin tension a tiny bit tighter.
Have you ever had correct stitches or is this a new thing?
Watson
Hi Watson - I have an update I've posted in an answer to OurWorkbench you might find interesting. Thanks so much for your ideas. While I don't think the shuttle tension was the problem (I'd got it as close to even top and bottom as I could using my "tension meter" (aka postage scales!) I think you were on to something and the problem was mostly likely under the bed. Kind regards... Megan