We traced an issue with symptoms that seem very similar to this to RoonServer failing to communicate what port the speaker should use to send control messages back to RoonServer. Here’s my most reduced version of the symptoms:
- If I play to one, and then start playing to the other, the second one plays silence
- If I play to one, stop, and immediately start playing to the other, the second one plays silence
- If I play to one, stop, wait 5 seconds, and start playing to the other, the second one works
In our experience grouping or not grouping the two zones doesn’t change anything, it’s purely about timing and ordering. This doesn’t happen with all AirPlay speakers, and I believe the Apple TV is not normally effected, but it could certainly trigger the problem in other speakers.
@Suedkiez, can you try some of those sequences with the NDX2 and Apple TV and let us know if the symptoms seem to match?