[TLDR] try changing your ATV4K Settings > Video and Audio > VIDEO: Match Content = Off to see if it reduces or eliminates this Dolby Atmos issue (even though such a video setting seems unrelated to an Atmos audio problem). Read on to learn the genesis of my theory.
So I just participated in a thread where the OP's issue was Dolby Vision-related, and the fix/workaround was to set the ATV4K's default Video Format to 4K Dolby Vision, and to set the Match Content Range and Frame Rate settings to Off. Doing so prevented the OP's LG TV from switching video modes in the middle of a Dolby Vision-encoded program.
I was reminded of this thread and it occurred to me that when dynamic range shifts between [Dolby Vision-encoded] scene changes cause the ATV4K (with the Match Content settings switched On) to make a TV switch video modes in the middle of a program, these same video stream events could easily cause burps in the [Atmos-encoded] audio stream playback (with varying effects depending on the AV components in use).
That's the theory. Perhaps this ATV4K Match Content behavior during Dolby Vision-encoded content playback might be the aggravating factor/trigger for [some of] the Atmos-related problems described in this thread.
Anyway, I scanned this thread and didn't find references to the ATV4K's Match Content settings, so I made this post to see if it makes any difference for all y'all :-).
PS - I have the older Apple TV 4K, an Atmos-capable Sony soundbar, and a cheaper LG TV that's merely 4K HDR10-capable (without Dolby Vision - so I couldn't test my own theory :-). FWIW, I've never had Atmos-related issues, so that sort of supports my theory because I've never experienced these Dolby Vision-induced video mode changes that might trigger them.
