On Harleys when you jump the rear sprocket with the belt, you will usually snap the belt at the same time.
If a belt seems tight to you, just imagine how far it would have to stretch to actually jump the teeth on the sprocket. Carbon fiber belts do not stretch, they will break as the belt tries to climb the teeth on the belt.
The only way in my opinion for the belt to jump, would be a VERY loose belt and then it would probably be jumping all the time instead of just on a hard accel.
My gut tells me that it's something else on the M3W causing the loud noise, not the belt jumping the teeth. Don't have a M3W and this is only my opinion based on my knowledge of other belt driven hard vehicles.
