Audio Async in 4K only...

Hi Everyone
This is my first post, so bear with me

Here is the setup i use:

ASRock Z87 Motherboard
i5 4670
AMD RX 460 4GB Ram
8gb Ram
850 Evo SSD
Windwos 10 Pro x64
All latest drivers and updates.
I have a 4k/60Hz Samsung 55" TV and the media Pc is connected trough HDMI 2.0 (as supported both by TV and RX 460)

Now here is my problem: I have installed the K-Lite Mega pack and i have played around a lot(including uninstalling and re-installing with different settings, Including/excluding LAV, FFshow, madVR,...), i have also tried the embeddded Windows Players and VLC without additional codecs. No matter what i do, all 4K HEVC Files are async with a audio offset that i can not correct (even if i set a manual audio offset in MPC)
VLC does not even H/W encode the file and the Windwos embedded player shows the movie but no audio at all...

The funny thing is however, it works perfectly with any x264 1080p .mkv file....

I am getting a bit frustrated, i can not make it work. Do you have any advice/tipps for me?

I have also tried passing the audio trough the 3.5 Headphone Jack instead of the HDMI, but no change.
Is it possibe the error lies in some setting for the tv refreshrate or anything?

thanks a lot!

LAV Audio decoder also has an audio delay option. Try that instead of the option in MPC. Although, the one in MPC should also work. You haven't enabled audio bitstreaming, have you?

Is the sync difference a constant value, or does it slowly increase during playback?

Are you outputting 1080p files as 1080p to the TV, or resized to 4K?

Maybe related:
https://www.reddit.com/r/xboxone/comments/59tuch/audio_lag_on_new_samsung_ks8000/

I have played around again with various settings. It seems that with the audio offset i can set in the LAV Audio settings it works. The only dissaointing thing is, taht the offset if different for every movie...

Is the sound early or late?

You could try the game mode on the TV, that reduces the amount of processing that the TV does on the video.