My challenge has been completed but isnt going away

I have completed the "Room to Roam" challenge where you must form a second island. Im now on my fourth island, waiting for my fifth to form, yet the challenge has not been considered complete, and is not rewarded me with my cash or dragon food. I remember when my second island was complete and i tapped "form" or whatever it said to officially make my island, the game froze, restarted, and when i brought it back up it had some error message, but my island was formed w/o completion of the challenge. Is there any way that i can fix it? Im on iphone 4 btw if that matters