I chased a belt issue for longer than I care to admit and it ended up being due to a wonky bolt hole. You'd torque it down and right at the end it would kick the alternator bracket out. I had to grind a spacer out of flat and never had another issue. It was so minimal you'd never would have guessed but it was enough. I believe the added friction, and thus the added heat, attributed to a premature alternator failure.