I have a Janome 1600P also and have the same problem on an older HandiQuilter frame. I notice when I am trying to do FMQ not on the frame that I can feel (hear) the threads popping thru the fabric when my timing is off with the needle. While I suspect some of that may be involved when on the HQ frame, I have been VERY frustrated too. Sometimes I can go multiple passes and sometimes only a few stitches. I know it must be a combination of the things mentioned, but I haven't figured it out yet either. If you do find the answer, pls post it.