Just one request. Please report back with the solution. I love puzzles and I watched this several times.
A completely subjective guess - sounds like the belt not fitting over the teeth properly, or else something is touching/rubbing the wheel or tire.
Assuming you made this on a center stand or jack, obviously its not something on the tire surface like a pebble in a sipe.
Looking at the white marks on the belt as they pass and correlating that frequency with the sound, its not one particular position on the sprockets or belt. The noise is too frequent.
Is the belt attempting to ride up on the rear sprocket on one side? Misaligned? I have an SRS, on mine there is a flange on the rear sprocket that if you had the belt far enough over on and pressing on, it would flap around against. There's supposed to be a small gap on the belt between the belt edge and that flange on my bike ( there is ) . Is yours like that?
Also I would examine the belt for missing/frayed bits or stuff embedded in it.