Hey all, hoping somebody has some tips to troubleshoot this really odd problem I'm having since swapping out my Arc for the Arc Ultra soundbar.

I've been trying to troubleshoot this all day and feel like the culprit of the issue I'm having is the TV. Here's my setup:

LG 65" C1

AppleTV 4K

Xbox One Series X

PlayStation 5

Sonos Arc Ultra (plugged into eARC port)

I noticed that when I swapped out the Sonos Arc to the Ultra last night (where I literally just swapped it out; using the same HDMI cord which always worked perfectly with the Arc), suddenly my Apple Music wasn't playing in Atmos and my Netflix was playing a show that I know supports Dolby Digital 5.1 was only showing in the Sonos app as Stereo PCM.

I did a lot of troubleshooting today, and unplugging and plugging back in of cords, etc. I feel like the issue is with the TV changing the signal from the eARC port somehow.

I think this because I just did a full unplug of the Arc Ultra power cord and HDMI, and also unplugged the HDMI cord from the C1. Powered off the TV, powered it back on, and then plugged everything in.

After that, I tested out a Marvel movie that supports Atmos and a song on Apple Music that supports Atmos, and everything looked great.

Then, about 10 minutes after doing that, my TV screen went black for a few moments, and when it came back, that same content started playing in only Dolby Digital 5.1. And now, in Apple TV 4k Audio Settings, Dolby Atmos content isn't even an option to select (whereas 10 minutes before, the Audio setting displayed "Atmos Available.")

I'm completely lost on what setting could be changing the signal (and have posted on Sonos and the AppleTV subreddits), but I'm also convinced it's my TV since when playing the same Marvel content from the Disney+ app on the tv didn't output in Atmos either, so I don't think it's the Apple TV.

This was long-winded, so sorry for that, but any help is appreciated if anybody has had a similar experience.