A new update of the iPhone app is now available in the App Store. It eliminates issues with the current iOS version. Maybe you need to reboot your iphone for changes to take full effect.
Unfortunately, we have found out that there are still problems with the iPhone 4. Newer iPhone's are not affected.
Please let us know if you have any problems with the app. For this purpose, send us an email to support(at)clockodo.com.