Small Appliance Repair Questions? Ask a Technician ASAP
Firstly, does the bobbin case appear damaged in any way? If so, it may need to be replaced.
To create the buttonholes, try using the zig-zag foot. Let me know if that works...
Have you checked if the needle is securely fitted?
Have you tried fitting a replacement needle?
Have you cleaned out any buildup of lint around the mechanism?
This can happen if the bobbin doesn't fit into the case correctly. Are you using the correct bobbin for this machine?
If you're sure the bobbin is correct (the machine uses a very specific bobbin, it's not interchangeable with any other bobbin class and using the wrong one can cause the problem you're describing) then it's definitely time to take it to a repair tech and have it looked at.