Usually if bobbin is jumping it is because of a rough spot on the case that is catching the thread Take it out and run your finger around it and feel for rough spots.

I have had customers with this complaint. I sewed while pushing down on the back right corner of the plate. Usually this stops the message. If it does I just go in and raise the sensor. I think consta

craftyqulters@rocketmail.com

What do you want to know maybe I can help