I don't have a Bailey but when I get birds nests it's from a poorly wound bobbin or not pulling up and holding onto the bobbin & top threads when starting off. I was taught to pull the bobbin thread to the top then wind it and the top thread around a pin a couple times and put it in the quilt to hold & mark it to be knotted and pulled into the sandwich later. Not putting the presser foot down will also cause birds nests but my machine has a safety feature that won't allow it to sew if the foot is not down so I've never had that problem. I'm sure I would if not for my machine being smarter than I am--LOL!