Bug VideoPlayer stucks and stutters and is async on Android 10, 11

I know there are some threads related to this, but not mentioning Android 11 or other new API levels (>=29).

I tried everything to play short videoclips (512x512, 4 seonds) loaded from streaming assets in an achievement overlay popup. It works fine on Windows editor and iOS but Android is a nightmare.

The videos are in sync for the first few frames, that audio skips frames and from then it stays async.

What I tried so far:
1. Using different codecs, H264, H265, VP8 (webm)
2. Loading videos from Resources (w/wo transcoding)
3. Using direct audio output and with audiosource
4. Unity Versions 2018.4.14, 2019.4.13, 2019.4.15, 2020.1.15
5. Toggle skip frames on drop, wait for first frame
6. Change video and applications framerate to fit to each other
7. ... a lot more I can't remember

But it stays as it is. All my videos are skipping words when showing up and are async.

There are console outputs everytime I play those clips:

AudioSampleProvider buffer overflow. xxxx sample frames discarded.

Is there something I missed? What are the best options for using video clips on Android (Codec, Frames, Settings?)

Kind regards