You won't get thread pieces in the bobbin mechanism if you always stop the machine with the needle in its highest position before you remove the fabric and snip the threads. Think I read this somewhere.
Originally Posted by
tessagin
If your feed dogs are in a down position, I would try to take the needle out. Maybe needle is broken/bent and tip is stuck. Also if you undo the screw on the needle plate, you may be able to see better why the needle is stuck. Have you checked the manual trouble shooting page?