Used NH 644 with balecommand; always used net but trying to use some string. My problem is when the monitor is on String/Auto the full bale alarm goes off and monitor goes into tie but the arms never move. It then shows error and full bale light flashes. The arms can be moved with the extend and retract buttons. The diagnostics show it is picking up the magnets. I am at a loss as to what to check next; any ideas?