Screen blinks on and off during calls

[DeputyStankus]

My TP2 has an annoying habit of randomly turning off the screen during calls.

Note that this isn't because I'm tripping the proximity sensor. As an example, I will call some customer service line, take the phone away from my head to dial in menu options, and the screen turns off at random intervals while I'm using it. I essentially mash as many numbers as I can, hit the power button to turn the screen back on, start mashing again, and repeat.

This doesn't happen at any other time except for during calls. Little help?

I'm running Sprint stock 6.5. Thanks!