Hi Sam,
No I do not have any AV1 decoded files. The movies which are sttering/dropping frames.or getting out of sync with audio are x264 and HEVC encoded bluray rips in 1080p or 4K. I had very poor quality picture with a 1080i TV movie film, probably because it was interlaced.
My 25fps low res MPEG2 EU DVD movie rips (or xvid avi’s) never played flawlessly until I’ve turned off the hardware acceleration for this resolution and set to HD and higher.
At the time when I bought my Vero 4K+s, they were playing nicely even DSD 2.0 audio, but now it seems they struggling with nearly everything, hires audio and movies as well.
With regards the movies I can see dropped frames or in every few seconds - like when the video is panning horizontally, it just stutters for a few frames, etc.
I’m not sure if any above information could help in debugging, but thats my experience now. And when my wife says its annoying then its annoying 