Stability sometimes can be an issue. We are working these small devices quite hard, and over time they can wear down.
On older devices once a week and on new devices, once every two weeks some users folks have had a great deal of success cleaning the devices out to give them a clean slate.
If you have Apple iOS devices:
Soft reset both devices: << This is usually the most effective thing that you can do.
Keeps all of your data but cleans out your device.
Note: iOS 7 devices use the Down-Volume and Power buttons simultaneously.