Help Back arrow screen key not working

[Android Question]

I have a new Samsung Galaxy S6 active that is running 5.1.1. I have intermittent issues with the on screen back arrow in the text message app and Facebook so far. It actually is not working within the settings menu as well. I can stop the apps and reopen with no change. If I restart the phone the everything works fine for a while. The manual back button works all the time so this isn't a huge issue. By the way I have switched from portrait to landscape to see if it is a temporary dead spot on my screen and it does not change the function at all.