It's not a bug. Bungie said it was a mechanic in the game. It's a 2 second cool down on the sprint. Also play cod or some other game similar, and make sure your left analog stick isn't broke. I had to replace 2 controller to the same damn problem. When you sprint, your guy just stops suddenly for no reason. That's how you can tell the difference between Bungies mechanic and your actual analog stick being broke. I did however manage to save one of the controllers by fixing it myself.