Check by swappnig the plugs between Reel 2 and Reel3 and see if the error stays on 43 (Reel 3 now spins on startup but reel 2 doesn't) or moves to an error 42 (Reel 3 still doesn't spin but Reel 2 does).
If it moves to 42, then the reel motor is most likely bad and needs to be replaced.
If it moves to 43, then you probably have a bad controller chip on the game board. Here's a thread where I fixed one that should help you:
http://newlifegames.net/nlg/index.php?topic=10912
OOPS - saw you already tried swapping connectors. Sounds like a failing motor...