They replaced the tensioner with the belt. I am lucky because they have theirr warranty with parts installed there. They even gave me a free loaner. But it was still strange that it happened.My guess would be the tensioner as well, its likely that even if the bearing feels good, the shaft the tensioner rotates on is worn and misaligning that way.
The rubber in the crank pulley can also get old and allow the pulley to move from where it should be, so look in via the wheel well to make sure its where it should be and not wobbling when the car is running.