One of my apps has starting misbehaving recently for no obvious reason, so I suspect that one of its data/settings files has become damaged. How can I delete the app data so that it's back to a clean slate? If I hold on the app and press X then the message states that both the app and its data will be deleted. However, when I sync the app back onto the phone, the data (account name etc) is still there. I've turned off "Documents & Data" in iCloud so it's not coming from there. I suspect that iTunes is being "helpful" and copying the data across from my latest backup but I can't figure out how to prevent this. What should I do?