I did some more testing with the ARC ultra and QN93 with surprising result.

I already swapped the oem Sonos HDMI cable with a used one (unbranded) but I now bought a new HDMI premium cable to 100% rule it out (certified blabla, see link below) and no more sound cut! I did not believed it but it's now almost a week without issues. Kind of crazy OEM Sonos cable is such poor quality. I checked it twice but for me the issue was really the HDMI cable

https://www.hdmi.org/spec/premiumcable

And have you tried watching content with uncompressed Dolby Atmos like TrueHD or tried gaming on a console like the PS5 with Dolby Atmos enabled and tested if (with the new cable) the sound still drops out?

Why are Sonos not responding on any of these issues ???

it is set to bitstream input and now also set to pass through output. same sound glitch 

Because this is a community site, and not an official ‘communicate with Sonos’ site? And likely the only Sonos employees that do exist here are busy moderating the forum?

I now tried with another certified Ultra High Speed HDMI cable. The first one was a Belkin. Quite pricey… but still had dropouts in sound with uncompressed Atmos content. 
I bought another one, also certified. It was almost an hour without dropout in sound… but eventually it happened again. 
So which cable did you try?

Kind of mind-blowing the type of cable makes a difference... Sorry don't have the package any more but this is the label:

For me the issue was on an external hdmi source and also Netflix internal tv app with or without Dolby Atmos didn't matter but never had one drop after the cable change and I'm quite sensitive to it so I'm sure for me it's fixed now

I noticed today, that the sound drops out when streaming as well. I noticed after the drop out output has changed from HDMI-eARC to HDMI. 
 

I think the problem with Samsung is that there’s no way to force eARC on. There’s only Auto and Off. 

I really wish there’d be a fix…

I tried troubleshooting with chatGPT today. 
We talked about Input Signal Plus on the TV:
 

“Key Points

1. Input Signal Plus Disabled Does Not Affect eARC Audio

• eARC is designed to work independently of Input Signal Plus. Disabling Input Signal Plus on the eARC port will not limit its ability to transmit high-quality audio (e.g., Dolby Atmos, Dolby TrueHD).

• This is because eARC uses a separate, dedicated protocol and bandwidth allocation for audio, unrelated to video enhancements.

2. Input Signal Plus Enabled Can Introduce Complexity

• Enabling Input Signal Plus increases handshake complexity because the HDMI port now negotiates for both high-bandwidth video (Input Signal Plus) and high-quality eARC audio.

• While this increased complexity doesn’t inherently break eARC functionality, it raises the likelihood of:

• Handshake errors if the TV or soundbar firmware isn’t fully optimized.

• Cable-related issues if the HDMI cable isn’t capable of supporting both high-bandwidth video and eARC simultaneously (though you’ve mitigated this with your certified cable).

Does Enabling Input Signal Plus Increase Risks?

Yes, enabling Input Signal Plus on the eARC port technically increases the risk of handshake or stability issues because the HDMI port now negotiates for both video and audio, even if you’re only using the port for audio. These issues may manifest as:

• Intermittent audio dropouts.

• Fallback to lower-quality audio formats.

• Handshake delays.

However, in your specific setup:

• You’re not sending video through the port, so the negotiation for video becomes less relevant.

• You have a certified Ultra High-Speed HDMI cable, which eliminates most cable-related risks.

This makes the likelihood of issues in your setup much lower, even with Input Signal Plus enabled.

Should You Enable Input Signal Plus on the eARC Port?

Here’s the recommendation:

1. If Input Signal Plus is Disabled:

• eARC will work perfectly fine. Dolby Atmos and other high-quality audio formats will transmit without issue.

• Disabling Input Signal Plus minimizes handshake complexity, reducing the risk of rare errors.

2. If Input Signal Plus is Enabled:

• eARC will still work as intended, but the handshake becomes slightly more complex due to the added video protocol negotiation.

• With your certified cable and modern devices, the risk of problems is small but not zero.

Final Answer

• Input Signal Plus Disabled: Safest option with the least risk of handshake issues, and it will not affect eARC audio quality.

• Input Signal Plus Enabled: Works fine in most cases but introduces a small chance of handshake errors. If any issues occur (e.g., audio dropouts or delays), disabling Input Signal Plus is an easy fix.

If you’re not using the video features of Input Signal Plus on the eARC port, there’s no practical reason to keep it enabled, as it won’t improve audio performance.”

Have any of you tried disabling Input Signal Plus on the eARC port and see if it helps?