If I make some changes on the SD card with Humminbird PC, but fail to delete the existing waypoints before putting the card in the machine, I'll get duplicate entries. This is more of an annoyance than a bug since you can always fix the problem my deleting the waypoints in memory and reloading the new ones from the card.
But this is a different problem. The unit numbers each new waypoint created by the "Mark" function sequentially. It seems that if you delete some of these waypoints it will start naming additional ones starting with a lower number. The result is different waypoints with the same name rather than duplicate waypoints. That is a bug, since it can't be fixed other than by giving the waypoints different names.
Has anyone renamed any of your waypoints created by the mark function? For example, if I changed the name of my final mark created waypoint from S00045 to say "rock3", would the next mark created waypoint be S00045 again or S00046?