I have both a 15" Bailey, and a 13" Bailey, and love tbem. There is a very active Bailey fb group if you need help quickly. The first thing l suggest is to remove the tiny " o" ring on the takeup lever. ( that is there to keep thread from popping out...but often catches thread) lnstead, l thread the takeup lever left to right ( yes, backwards!) This means you may need to loosen top tension a very tiny bit.
Most new owners of these machines forget to put down the presser foot and run into problems that way. Others find that thicker cotton thread's the culprit. If you've already tried new needle, oiling gears behind bobbin race, and checking thread path, then l suspect the quilt's too high off the machine's bed. Try lowering the bars so the quilt just skims the bed...and not tight as a drum either.