Display > HDMI auto adaptation

[DMD]

Good evening
I connected the HDMI output to the sintoamply input (Yamaha RX-V775) that supports 2160p @ 30Hz, in the HiMedia box (fw 2.0.4) I selected HDMI auto adaptation.
This selection does not remain and the box returns to 1080p @ 60Hz, so I have to set it manually, this could be fine.
But I've noticed that sometimes this value is changed to 1080i @ 60Hz, and I do not understand why, maybe I have to connect the HiMedia directly to the 4K OLED display?
But in this case I can not decode the HD audio stream through the sintoamply.


Thanks for your suggestions