Server Version#: 1.41.0.8994
Player Version#: 10.21.1.1562 (a9d06cb5)
So - this topic is drives me mad.
My setup: Samsung Q90T with it’s native app plays videos and sound absolutely fine including Atmos with no audio dropouts. Since it’s awfully slow I changed to Fire TV stick.
Sound goes out to a Sonos ARC. I also used an HDMI eARC Audio-Extractor to not give any sound to the TV and therefore eliminated CEC issues or Audio-Passthrough on the Samsung as root cause. Since sound plays fine from Samsung to Sonos I also elminated that issue.
Other apps like Netflix and Waipu.tv work fine with the Fire TV stick to Sonos.
Now, whatever video material I play (direct play audio and direct play video) from the stick (stable 250Mbps+ connection via 5GHz wifi network, also tested with Ethernet adapter at 80Mbps+ connection) I get audio dropouts or roughly a second every 5 to 10 minutes. Only solution that worked was setting Fire TV to “Dolby Digital” and therefore not having Atmos available anymore. I would understand if it might be related to only multi-channel sound but it’s also in other files… 
Key question: Am I the only one with this topic on current Fire TV 4K Max and is it a known issue with the Plex App? If so I would return the FTV + Audio Extractor and give up; although I totally like the setup that finally allows me to play any format on the Sonos Arc; but the dropouts make it a mess.
Plex server is a Synology DS920+ running Plex on official docker image, connected over 1Gbit/s (tried both ports with individual cables - no change at all).
I use other sticks on other TVs with no problem there (no soundbar attached there) but as soon as I put older FTV sticks (4k, 4k Max first generation) to this setup the same problem occurs. Again - no issue with native Apps and the sound is looped past the TV directly to the soundbar. Sonos support could not find an issue in the logs I created…
Thanks a lot for your feedback!!!
