You say it’s definitely not the belt. Why do you say that?
You could also have a bad bearing or a bad motor.
I might suggest you have it looked at by someone local. If it’s only 2 years old it may be worth repairing.
It sounds like something wrong with the tensor that the belt is attached to. Obviously something is dragging and keeping it from operating properly. Its possible, but unlikely the belt is not installed properly. If not, check this site to see if you can get some more clues. -