Singer 2010 bobbin winds UNDER bobbin?

Hello,
I just bought a used Singer 2010 with the wind-in-the-case bobbin. When I tried to wind the bobbin, it engages, but the winding takes place UNDER the bobbin, with the thread never even getting around the bobbin. I have changed out bobbins to a new one, tried everything I can think of, but to no avail. When I slide the little arm over the bobbin, I checked to see if the small bar under the bobbin comes up to engage the bobbin, and it does, but it simply winds under the bobbin, around that little bar. Do I need a new casing? Could it be the gearing? Thanks for any help you can give!