https://online-go.com/puzzle/20781 Only lets you finish the ladder in one direction and marks it as incorrect if you try to turn the ladder towards the edge at move 11, (which is a valid way to capture a ladder.)
I guess your best bet is to try and contact the puzzle creator…?
Perhaps someone more knowledgeable than me can help?
1 Like
Hope @alexx speaks his languages well. 
The autor is 
Profile: https://online-go.com/player/831306/
1 Like