Belt keeps riding to the side

No matter what I do I've followed the tutorials to a t. even with the guard on it does this ( so much so it wore through the guard) the motor is tight the belt has a little bit of play and deflects slightly
I am aware the belt is ****** I haven't rode it more than a few hundred metres after I noticed it the board isnt even a week old I've ordered new belts and belt guards but if anyone has any ideas I'm all ears

 

After some troubleshooting it's definitely just the belt that causes the issue but what could have caused it in the first place?

 

Video file won’t play for me. I’ve had no belt issues on my GTRs except briefly when I rode in soft sand. That went away and belt was fine after moving it back off the tire, after dumping the sand out.