Originally Posted by
elnan
No matter how new or old, every sewing machine I sit down to, I hold both top and bottom threads out the back until several stitches are made. It is just the way I learned to sew. I have a small herd of Kenmore sewing machines, so am interested in knowing which models are acting up.
I still hold thread tails as well! I would certainly start with a good cleaning of your bobbin area. Use a flashlight. Sounds like you possibly have a tiny bit of thread stuck somewhere. A friend had that happen on a vintage singer and it caused all kinds of issues. Found the thread bit, plucked out with a pair of tweezers and problem solved.