My first thought was the thread was hitting a snag somewhere along the path. Since most thread is now cross wound and your machine is horizontal, it isn't catching like on the notch that the old spools had.
Have you changed the thread and needle? I have heard of needles that have a burr in the eye. I know that sometimes the troubleshooting guides in the manuals aren't that helpful, but perhaps there is something on page 81 of the pdf might be helpful. It is hard to troubleshoot when the problem is random.
Janey - Neat people never make the exciting discoveries I do.
Last edited by OurWorkbench; 03-11-2022 at 06:12 AM.