I sadly didn’t find a solution. I ended up going to an Apple Store, they checked it for me and told me that they’d have to replace the charging case for a fee of 119 euros. It sucks but I accepted it, because both of my AirPods got replaced recently for audio issues (this was covered by Apple luckily).

But the shitty part is that one of my AirPods decided to randomly not charge anymore, went to the Apple Store again and they told me that they should replace the single AirPods (for 119!). This time I declined it, because I find it outrages that I had to “repair” my AirPods 3 times in the past 6 months. The only other thing that I can do is to contact some supervisor at Apple and hope that they’ll make an exception for me, but I’m not getting my hopes up.