It happened a couple of times on my Brother Sewing/Embroidery machine. First time, it turned out that I had a small piece of thread up in the take up lever area. I did everything you did several times. Finally, Hubby took the head cover off and found the errant scrap of thread. Another time that the bird nest happened, the thread was catching on one of the thread guides. I solved that by using a thread net to keep the thread from pooling. I use only cone threads (1000m to 5000m) on the Brother add on multi cone stand. I still have to be careful how I follow the thread guides to allow my machine to go to the needle without presenting problems. Sometimes I have the thread wrapped around the bobbin winder then to the take up lever, sometimes I can go straight. Whatever works!