Slow to respond back button
I have a brand new iphone SE, purchased 3 days ago on 10/14/16. When I'm in a text, and I want to go back to the main lists of texts, the "back" arrow is slow to respond. It takes 2,3,4 up to 20 times to press it to go back. Apple has reloaded the software, with and without restoring, and the problem remained. We switched the phone, and it still happens. Their best guess is a glitch with the software, but they haven't heard of it happening to other users. Does anyone else have this problem?
iPhone SE, iOS 10.0.3, Back button in texts