are you 100% sure its not from the spark plug wire boot? if it was me I would not ride it anymore then I needed to till I fixed it because these CDI are weak and there is a possibly that a stray spark could short out your CDI.
try changing spark plug maybe the plugs insulator is bad. I have one question you can see the spark jumping to a fin on the head right? and not jumping from boot to plug. Im not doubting you just trying to point out things I myself have missed in the past.