Hi, BuddyG!
Is your Magma a clone or authentic? I do have an o-ring on mine also, but it sits behind the afc ring. Yours looks to be above it so that the top cap doesn't appear to screw down all the way. I didn't have leaking from the airhole itself. Mine was the condensation dripping behind the afc ring. The o-ring alone fixed my issue. An interesting modification though. Thanks for sharing.