Well, without a lot of context to go on, I'll relate a similar experience with my 111W class machines.
I was having on and off problems where the bottom stitches would get tangled and the workpiece would pull out from under the needle hard. There would be 2 or 3 strands of thread coming out of the needle plate.
Finally I noticed that when that happened, my needle thread was split on the hook. It turned out I was holding my threads back way too hard when I was starting to sew. I only hold back lightly now and haven't had a problem since.
You'll see advice here to "hold the threads back hard". But I think that applies to larger machines, like the CB4500 and such. Maybe someone else will comment.