the bottom bobbin threads keep wanting to make their way up to the top surface. even when i have the top tension adjusted either way. i called a sewing place that works on machines and they said to tighten the little screw a fraction and that should fix it. he said you aren't really ever supposed to have to adjust that but sometimes it will help. it did for about a year but now i am having trouble again and the adjustment isn't working at all. i might just go ahead and birng it to him to fix at the shop. they are really good there but just wondering if there is anything i might have missed trying myself....thanks to anyone who can help...carla