I have been having all kinds of trouble while putting together a puzzle quilt top. Missed stitches, bunched fabric, chewed fabric, you name it. Rethreaded machine, rewound the bobbin and put back in, changed needle again. Just for fun after a lot of pirate talk I took off the walking foot and put on a plain one - worked like a brand new machine! Does a walking foot wear out? Is there something I should be adjusting? I'm stumped.