no sound from apple tv app on android tv - just trailers

I'm running the Apple TV+ app on an Android TV streamer. I only get sound when I play trailers - not the actual movies or episodes.

I believe that the audio format of the trailers is different than the one of the movies/episodes and this is why my relatively old TVs cannot play it properly. I am unable to control the audio format on the Apple TV+ itself - there is no settings menu entry that enables it.