I have a Singer Ingenuity 4-5 yrs old, I have no idea why but sometimes all of a sudden the top thread snaps, loud and hard right at the needle. In the bobbina area somewhere there is always a piece 1-1/2-to 2 inches long bent into a sharp V. Sometimes it does it over and over in one session and sometimes it may be days before it does it again. It doesn't matter what foot, thread, needle, fabric, it just happens. I still like it tho! I think she just gets moody, like me.