Why is my back button and app replace button not working?

[AC Question]

Had the phone for about 5 hours now and was working fine until it dropped under 10% for the first time and now the back button and app replace button wont work. Touch screen and all other functions are fine.

 

[B. Diddy]

Welcome to Android Central! Which phone? The battery dropped below 10%? Have you tried charging up, then rebooting?

In general, don't let your battery get below 30-40% on a regular basis--it can shorten the overall lifespan of the battery.