I think I've uncovered a bug in the eARC handling. It seems very unstable with the audio output being completely wrong at times.
Dolby Digital+ tracks from Netflix suddenly only play in Dolby Surround (2.0). I have to turn the TV off an on again to get the DD+ output.
Right now I'm watching a movie on cable that has a DD+ soundtrack, which worked just fine. During the commercial break the audio on the channel changes to 2.0 output, yet my receiver still receives DD+ (the "Audio" button on the TV remote shows that the audio on the channel is "multichannel" when the movie plays, and doesn't show the multichannel symbol during the commercial break). I go one channel up and back again and the receiver shows 2.0 again. However, when the movie starts after the commercial break it doesn't switch back to DD+. Going one channel up and down again gives the correct audio output.
My audio receiver is obviously set up correctly as I get sound from my speakers (and not my TV), and it is in proper surround when the TV sends the correct bitstream over eARC.
It would be nice to get confirmation of this, and maybe even some fixes if there are any.
EDIT:
Additional testing results. I went to a cable channel with dual audio: One normal, one multichannel. If I'm switching between them the switch to and from DD+ works just fine. So if the selected stream changes from multichannel to normal, the TV does not discover this change and keeps the output in the previous format. If you do that change manually, it is discovered and output properly.
However, even if I can correctly get DD+ audio from cable channels, the built in Netflix app won't output DD+ (even after a restart). It has done so previously, so obviously something is messed up with eARC, and the most likely culprit is the TV (as my receiver does indeed receive DD+ from the TV... sometimes)
