It had me totally bumfuzzeled until I saw a post on Humminbird Facebook page by a guy telling someone how to update his unit. He told him to be sure to delete any previous .bin files on his card. He didn't say why, just to do it. That got me thinking and I checked my card. Sure enough, had 2 .bin files......I deleted the older one, plugged the card in, it went though the update process, and found the Tducer! - worked ever since!