Is anyone else having trouble playing 4K HDR + Dolby Atmos content from the Apple TV app? When I launch a stream, it plays back smoothly for about 3-5 minutes, then the audio drops outs (to silence) for a few seconds (video is fine); audio returns briefly and playback is normal for another 30ish seconds; then the video and audio both stutter for a few seconds; then playback pauses and buffers. From there on, it will play a few seconds at a time and then pause again to buffer. Switching to a different title starts the process over again: 3-5 minutes are smooth, then issues start. I do not recall this happening before the Apple TV app update that enabled Dolby Atmos.
Hardware is 4630X running latest build of the OS (9.3.0 build 4170-29) and Apple TV app (4.0 build 101) available for download. Wired connection to Gigabit Ethernet network. 120 Mbps service from Comcast. Roku speed test reports 80-90 Mbps downstream.
Nothing ever buffers on other Roku apps; however, I understand that Apple can run a higher bitrate (25 Mbps average) for 4K HDR compared to most other providers (around 10-15 Mbps average) - but that may only be on the Apple TV 4K device and not applicable to Roku. As far as I'm aware, the only other service capable of running bitrates in the 25 Mbps range is Movies Anywhere, and I don't have any stuttering/buffering issues with Movies Anywhere running 4K HDR + Dolby Atmos on Roku.
EDITED 8/10/2020 to add Roku OS and Apple TV app versions.