Occasionally, an app can go into an unstable state when the iPad has not been turned off for a number of days or when you’re running lots of apps and have not shut any of them down. The most likely cause is not enough memory to run the application. When this occurs, I recommend doing the following:
Close the App:
Double tap on the Home button. This will display all of your apps that are running at the bottom of the screen. If you press down on one of the apps, it will start to wobble and display a red circle. If you tap on the red circle, the app will close. If you have a lot of apps running, shut them down one at a time.
Shut down the iPad:
Tap on the Home screen and the On/Off switch for 15 seconds until the Apple logo appears on the screen. Then wait approximately 45 seconds for the iPad to reboot. Tap on the app and relaunch it.