You say it works on the PC and Oppo. Which player are you using on the PC? Kodi?
VLC and MPC
I’ve tested the clip with my Windows test setup and I can confirm this is definitely a Kodi issue, not OSMC specific: both Vero and Windows behave exactly the same when playing the clip back via Kodi… The German track plays fine without passthrough, decoded to PCM, but fails to play with sound when enabling passthrough. All other tracks work just fine no matter what.
And the PC was connected to your AVR and you’ve used passthrough playback when using those players?
It is the same problem as in my thread. I guess we found a Kodi bug.