Beelink R68 Passthrough

Hello,

I have Beelink R68 box. Wasser 4.0.2 firmware installed (API 23).
KODI 17 from play store.
Using SPDIF passthrough (enabled in system) to my external dvd player.
Player have support decoding of ac3 & dts.
Sync to video is disabled.
If I enable passthrough in KODI I have audio only when only DTS capable received enabled. And receiver shows linear stereo pcm. No 5.1 audio. Stereo upmix is disabled. Enabling it changes nothing.
If I enable AC3 capable with/without transcoding then I don’t have audio at all.
Changing 2.0 channels to 5.1 in settings change nothing.

What should I do?