Yesterday I was replying to an email from the native stock mail app. When I selected reply or forward, it would freeze for several seconds. I had to back out of the email and go back into it to reply. Once I began typing my reply, I noticed the top of my screen flicker where my bars, carrier, time and battery icon are. It continued until I was done typing. I've never seen anything like this before. Has anyone else experienced anything like this? I'm running ios 7.1 on my iphone 5.