Hello everyone,
as a preface: I solved it already, I just want to post it here, so maybe it helps someone in the future and saves some of their sanity.
The problem I faced was that Unity always used a previously generated Soundbank, so new audio, events and whatever was changed were not reflected in the editor (and in the build). The weirdest behaviour I observed was that I even could delete the soundbank and it still was playing in Unity (the old version of the soundbank of course). At this moment I thought it had to be cached somewhere, otherwise how could it play even anything? I searched in StreamingAssets/Audio/GeneratedSoundBanks and in WwiseProject/GeneratedSoundbanks and afterwards in the whole Unity project (in my case the Wwise project is inside the Unity project) and did not find another saved soundbank. I found some posts on here and on reddit which described similar problems and tried their solutions to no avail.
THE SOLUTION: I deleted the soundbank and made a new one, which instantly solved the problem.
Maybe someone who knows the cause of this can chime in, I would be very interested! At the time i was playing around with compression settings and used Vorbis. I used an AkBank component with "Decode compressed data" and "Save decoded bank" enabled. Maybe it saved it somewhere and the caching system failed, so it always used the old one? And my solution essentialy is a cache buster?
Versions: Unity 2021.3.9f1 & Wwise 2021.1.10.7883.2429
Hope this can help!
Cheers