When Cannon captures the Rhino, the text "I win!" appears. But it's not a checkmate situation at all. What error is this?
When you do not explicitly specify a royal piece through a parameter royal=N, the diagram assumes the last piece in the list is the royal one. In this case that is the Rhino. By default the diagram assumes extinction royalty. So when the diagram captures the second Rhino, it assumes it won the game.
Either re-order your piece lines in the diagram definition so that the King is last, or add a line royal=8.
When you do not explicitly specify a royal piece through a parameter royal=N, the diagram assumes the last piece in the list is the royal one. In this case that is the Rhino. By default the diagram assumes extinction royalty. So when the diagram captures the second Rhino, it assumes it won the game.
Either re-order your piece lines in the diagram definition so that the King is last, or add a line royal=8.