Life In 19x19

I have been playing through tsumego on SmartGo Kifu, the iPad app. It presented me with this problem from GoProblems, today (GP6704)

Click Here To Show Diagram Code

[go]$$B Black to Play and Live
$$ -----------------------
$$ . . . O X X . . . . . -
$$ . . O . O X X X . . O -
$$ . . . . O O O O X X X -
$$ . , . . . . . , O O O -
$$ . . . . . . . . . . . -
$$ . . . . . . . . . . . -[/go]

Intriguingly, SmartGo considers this to be a 7 kyu problem. Anyway, so I gave it my solution:



It responded at but told me that my response at was incorrect! What? Why?

It seems to want this solution:



But, from what I can see, my solution is generally better because its solution has a Ko threat at the marked point.

Firstly, have I misread? Secondly, how does one go about correcting incorrect branches on GoProblems?

http://goproblems.com/6704

Two people have commented on this at the problem page. It's been marked "needs fixing", I'm not sure there's much else you can do.

The quality of goproblems.com is bad enough that you have to question most things you see when you try the problems for their answers. Just keep an open mind if you use them.