Default [Q]

So I've been using my HTC one for about half a year, however most of the time when i call someone or answer a call, my HTC one keeps pressing the back button. To make sure, i turned off power safe so the buttons would vibrate when pressed. When i tried calling someone with power safe off, the moment i hit call, my phone constantly vibrates as if the back button was constantly being pressed. I tried a factory reset and nothing helps. I don't know if i should send my phone back or if there is a solution to this.