No audio HD with 4k 60Hz

When playing videos with hd audio on 4k60Hz, via external HD, I have mute audio… just a quick static noise (despite the receiver accuses Dolby HD or DTS HD ma on the display). I already checked the passthrough option, and unchecked the sync playback). DD+ and DTS passes ok.
When I change to 30 Hz, the audio HD passes ok.
I am using:
Box Alfawise H96 pro+ (amlogic s 912)
Receiver Denon AVR x2100w (Dolby HD etc ok, no Atmos; HDMI 2.0 HDCP 2.2)
projector Viewsonic px727 (4k HDMI 2.0 HDCP 2.2)
When playing direct via box/android/kodi, the results are the same.
What can be happening?

I will answer to myself, maybe somebody can undestand what happened ( I did not).

When I changed the resolution display (box) from YCbCr 4:2:2 10 bits, to 8 bits, suddenly the sound HD passthrough was ok.
In 10 bits, when in 4k60Hz, it blocks the audio.

So, with resolution 4k 60Hz YCbCr 4:2:2 8 bits (or also 4k 30Hz YCbCr 4:2:2 10 bits), the audio passthrough was ok and image goes fine, with much better results on 60Hz.

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