Leave it alone, it's not worth the risk unless the mylar is trashed, cracked or peeling. I had a HUO game and that had similar air bubbles starting to form, you don't notice it when the game is on anyway. If you remove the mylar you'll just start causing wear around the inserts. EVERY single BoP without mylar or Diamond Plate (and even some of those) has insert edge wear. It would only be a good idea to remove if you were going for the complete restore & clearcoat, but it's not worth doing that because you've got yellowing outside of the mylar area.