There are a couple symbols that come up on your Bernina.

One just comes on when you do so many stitches. To get rid of that one, you need to take it to the shop and have the tech re-set the service panel.

Another symbol indicates that the thread isn't bouncing in the check spring correctly, or "upper thread break." To fix that, remove the cap on the end of the machine and put the check spring back into position. That happens sometimes when the machine is going really fast, then stops on a dime.

I don't know of a "clean bobbin case" symbol, and I'm a Bernina tech. What does it look like?

Edited to add: There's also a low bobbin sensor on the B640, which the tech can turn off in the service panel. It can be particularly persnickedy sometimes.

Remember... if you sew every day, your machine needs to be serviced every year. But never go more than 3 years without a service. It may just be time for a service.

Have you considered that the bobbin in question might be warped? If you drop one on concrete or step on it, they get out of round and won't work correctly. Try a new one.

Marcia

I work with ladies at our church and we have about 16 machines and sergers. we also have a shop vac. I regularly use a soft pastry brush while using the vac to get out the lint.

I too have a Bernina......well I should say Berninas. I second what everyone is saying about the canned air. My dealer told me that is a big NO-NO for any of my machines. I would say your best bet is to take it in and have it serviced. That cost me about $90 for my 780, but I think it is money well spent for what I paid for the machine.

I have a 640E and was told to never use canned air or blow into it. You are just blowing lint deeper in machine. Time for service. Also, by blowing you may blow moisture into it. Good luck

I was having issues with my Bernina bobbin - turns out the bobbin was bad - mine have metal inserts and they were worn out causing my machine to have error messages. The fix was to use a different bobbin and throw away the worn out one. Hope the answer to your problem is that simple.