Hoping this isn't anything too serious, but I figured I'd check with the gurus here! My FW has started to make a strange knocking noise when I sew. It doesn't happen when I take out the thread and rev it, only when the foot is down and actively sewing something. Even then it doesn't usually start for at least a dozen or so stitches, and then comes in and out intermittently. I can't determine where it's coming from; at first I thought it was because my table I was using was a little uneven, and the machine could wobble, but after moving to a different part of the table I haven't found any improvement.
I've oiled her up good, and cleaned out all of the dust and lint I could find. Does anyone have any ideas what is going on?