I've used Google translate here so this might be me misunderstanding your issue here but the most recent cache you found according to your profile stats is GC94QHR (Wahnbeker Spielplätze - 5), since you found this cache on the 3rd of September it clearly has been updated and can't be the issue your talking about. Your most recent found can be found in the Milestones-section of the Profile Stats.
However, your youngest cache found is GCABA6B (Mit den Ottis bei den Alpakas) which you logged on 20th of August. This makes me think there might be a misunderstanding or translation issue here? The "youngest cache found" is not the most recent cache you found, it's the cache of all your finds which has the most recent hidden date. So if you attend an event that will generally be the youngest cache you've found, to change this cache you need to log a cache that was hidden between the date the event took place and today.
