Just a quick thought l have the same machine and couldn't understand what was happening and my machine was brand new so asked the dealer as my bobbin thread 3 spools was used up quickly in embroidery class and the white showing through it worked good when a friend loaned me her spool so the result was urgggggg when you thread up to wind your bobbin the first wind round on the top of the machine has to catch a tention spring so you pull the thread together and you can hear a little click meaning it is engaged so carry on wind your bobbin l hope you can understand my explanation