More than likely it's another app that is conflicting with it. Even Google Drive has caused problems on these tablets. You can try uninstalling the latest apps you installed or just factory flash the entire tablet. In rare cases it could be faulty hardware or faulty firmware/operating system.
It's a software bug. To fix it you will need to unplug the battery, press the power button for 10 seconds to discharge any capacitors, plug the battery back in, charge it (factory charger preferred) to 100%, then turn it on and enjoy. If this doesn't fix it then you may need to replace the battery. Watch this video for how to get the cover off the back of the Galaxy Pro and Note 12.2. https://www.youtube.com/watch?v=VeSG0hHp... This video shows you how to replace the battery. You just need to unplug it. Be careful with the connector while unplugging it when the battery stays screwed in.