I have some ill Magura Menjas (07) that need a proper service before they properly die due to total neglect.
Now I've had them open before but can't for the life of me remember how to get the rebound adjuster off on the bottom. The manual and service manual are no real help and I'm sure it's just the O ring holding it on and you just pull. I've tried that with a "small" amount of force but no luck. It's probably welded itself in but it still operates.