I think it might be an iPhone 5 issue. Tapatalk worked fine on my 4, but I've had the same issues as you since I upgraded.
Must be it. It's annoying how slow apps have been to update to at least accommodate the larger screen.
Oh then let me ask you this: do I need to pay for app again to download on my iPad? Or bc I paid for iPhone app, I'm good to go?
Tapatalk finally released an update for iOS6