Bernina Deco Bernette 340 embroidery machine grinding noise?

I am borrowing a friend's embroidery machine. The bobbin area keeps jamming with thread. The owner of the machine had a large spool of bobbin thread which seemed to be a different consistency than the previous that I was using.A needle broke, the bobbin area jammed with all kinds of thread and now there is a grinding noise coming from that area. I have taken the plate off, used the lint brush, taken the bobbin casing out and cleaned the area, then put a drop of machine oil in the area where the bobbin casing goes to make sure it wasn't a lubrication problem. Any ideas?