I just realized that my DD+ Audio (used as in almost all newer Netflix shows)is not decoced when set to passthrough. It is only working as PCM. My Denon AVR is capapable of decoding DD+ and doing so over Chromecast.
Is this a known problem? There are some reports over in the kodi forum, but mostly related to Windows or Android. In Windows it seems to be fixable.
How about libreelec?