I don't know how the bobbin could not be wound tight enough if the machine does the winding. And who knew there were classes on the BSR? I don't think I've ever heard of that through my dealer. I'm going to fiddle around with the bobbin today and see what I come up with. I do have a second bobbin case so I'll try using that one and moving the screw. I was told it was for "thread play" so I wouldn't have thought to try it for this.