I didn't read thru all of these answers, but after a quick glance I 'm amazed I didn't see more about the 830 and thread going backwards. Pulling thread backwards can also ruin the take up lever check spring. The 830 has an additional sensor on this spring which is attached to the spring with small plastic clips. Pulling the thread backwards can break the plastic clips disabling the sensor. You can turn off the sensor and sew normally should this occur, but you don't want to break anything in the machine.