If the bobbin winding starts when the thread is not passed under the pretension disk of the thread guide correctly, the thread may become tangled under the bobbin winder seat.
Stop the bobbin winding.
Cut the thread with scissors beside the thread guide.
Slide the bobbin winder shaft toward the front, and then remove the bobbin from the shaft and cut the thread leading to the bobbin in order to be able to completely remove the bobbin from shaft.
Hold the thread end with your left hand, and wind off the thread clockwise from under the bobbin winder seat with your right hand as shown below.