We were encouraged to buy a second case for our Pfaff 1475. We had classes on bobbin embroidery, and bobbin ribbon embroidery at the dealers. You HAD to futz with a case to do any of this. The Pfaff manuals also explain how to adjust tension.
I've had adjustment screws work loose and change the bobbin tension. If you have learned how to adjust, you can check tension before putting bobbin in the machine.