Hi @JonDD
Welcome to the Sonos Community, and apologies for the delay.
Thanks for your diagnostics - unfortunately they don’t help much as Sonos cannot tell if your TV is muted. I can see that the Beam was playing TV audio at the time the diagnostic was sent.
Do you still need help? I have to agree with @106rallye - I don’t really understand the issue you’re having. You want your TV to be muted, otherwise you get a weird echo effect. Do you mean that TV audio coming from the Beam keeps cutting out? If so, please unplug your TV from power for about 30 seconds and switch it back on.
Additional advice can be found on our TV audio stops or skips help page but if you continue to have problems, please get in touch with our technical support team directly.
"Common sense is the collection of prejudices acquired by age eighteen." - Albert Einstein