take the bobbin cover off and bobbin out--check very carefully for a thread that has gotten stuck somewhere. Clean it again and you didn't say if it's a drop in bobbin or front load (from the side) bobbin. Sometimes when we take apart the bobbin area and case it doesn't get back quite right and allow the bobbin to set in just right so that the take-up arm works correctly. so take out the case again (on drop in the part that the bobbin drops into) and re-clean and then fit back in. Hopefully this will take care of it.