I'd let the machine 'rest' for a while as well. The other thing you might check is to see if there is a teeny tiny thread stuck in the bobbin casing. Had that happen with a friends older mechanical machine where the tension was off. Granted, not same situation but something else to check. Also, on my friends Viking Sapphire, neither she nor I could her machine to raise the feed dogs once again after she had lowered them. She ended it up taking to the shop and all they did was move the needle with the hand wheel - problem fixed.