I’ve got a Sonos Beam here linked to an LG TV and it’s not doing this, or at least I’ve not noticed it. I assume you are using CEC and/or infrared to control your volume-level. Maybe try to eliminate things by switching off infrared (if not done already) and disconnecting any devices connected to the TV over HDMi that are also using the CEC protocol, just to see if you can identify the ‘culprit’ that's causing the issue. Of course it might just be your make/model of TV, but perhaps eliminate the other things mentioned first.

If, after trying these suggestions, the problem still persists, then it maybe best to submit a Sonos system diagnostic report from within the Sonos App, note it’s reference and then contact/chat with Sonos Support Staff via this LINK and see what the Staff can perhaps suggest to resolve the matter.

Thanks so much for your reply Ken. I won’t pretend I understood everything you said as I have little home theatre knowledge but I don’t think it’s related to me changing the volume on my tv or cable box as it is consistently changing the volume on the beam to 5. Whether I set it at 0 or 1 so I don’t hear it, it automatically increases it to 5 within a few hours. It’s like it wants to default the volume to 5 for some reason. And it happens regardless of whether I use my other sonos speakers or not. 

@klynn 
The CEC protocol allows you to use the TV ‘remote’ (or other ‘remotes’) to power on/off TV peripherals, adjust volume of the soundbar etc. so aswell as your TV ‘remote’, any devices attached to the TV HDMI ports that use the protocol might adjust the soundbar volume-level to 5% - so either disconnect those devices temporarily, or switch off CEC within their settings and see if the issue stops. If it does stop, you then know to take a closer look at each of those ‘other’ devices and you maybe able to discover which one is ‘perhaps’ causing the issue.

Similarly this issue could be caused by an infrared command to the Beam - so to eliminate that, simply switch off the infrared receiver in the Beams ‘room’ settings in the Sonos App and see if that stops the volume increasing to 5% - if it does, then you can perhaps go onto discover the source of the infrared signal… so it’s just a case of trying to narrow down the cause. Of course it might just be something that the TV is doing here, but it’s just too early to say. I was simply trying to help you eliminate a few things first and to try to narrow things down to perhaps help you identify the cause.

However there is the option to also go onto contact Sonos Support, but it may be easier if you can perhaps eliminate a few things first. It might at least help to reduce the time you’re on the phone to them, trying to get to the root cause. The Sonos diagnostic report may ‘perhaps’ help them to discover the cause too.

Thank you Ken, I appreciate the more detailed response and now I have a better understanding. I will try this tomorrow and see what happens. Thanks again!

Hope you can get it sorted… maybe let me know how it goes.