Apple TV Atmos bug on 3rd party apps: Audio format workaround needed

I've been dealing with the weirdest bug. My Apple TV 4K started playing up a few weeks ago, sending a stereo signal on any third party video app (but still working completely fine on Apple TV app content).

The only "fix" I have found so far is to

1/ open a video and start playing

2/ go into settings

3/ change the audio output to change format "ON" and Dolby Digital 5.1

4/ then open the video app again and play for a second

5/ go back to audio settings and change back the change format to "OFF"

Then it outputs again in full Atmos. But I have to do this every time I switch on the Apple TV.

My set up is as follows:

Apple TV4K connected to eArc on LG OLED G2 screen

LG OLED connected to Arc on Marantz receiver (Atmos compatible), set on "Direct' or "Pure Direct" (streams without any audio adjustments.

This has been my set up for 2 years and nothing has changed whatsoever, and never had any audio issues in the past.

I tried restarting the Apple TV, re-installing the apps, logging out and back in, and installing the latest firmware (I've also updated the firmware on the TV, although the fact it works fine with Apple apps makes me pretty sure the issue is with the Apple TV).

I do not understand why it impacts only third party apps, and the fact it can be solved with this little trick every time I start it is really aggravating. Clearly it can output in Atmos, it just stubbornly doesn't want to.

I've researched this one on these forums, reddit etc. and cannot find a similar issue being addressed.

I'm hoping someone here might have a fix?

[Re-Titled by Moderator]