I do have Fios One TV box from 2019. Few weeks back I bought sNew Sony 4K X900H, UHD TV and unable to get proper audio. Unable to get 4k Video ( may be I am not seeing any content yet). Have fios ultimate TV too. So there should be some channels with 4k content. Forget it. the audio was dismal too.
The default Tv audio itself was better on youtube, disney plus etc. i had the digital audio cable plugged but no improvement.
I then got the Sony HT-ST5000 7.12 channel sound bar and sub woofer to compliment My TV and hoping the audio / video issues would be resolved. In fact more audio issues now. It loses connection every now and then.
but as others have mentioned, switching between streaming apps with throw off Fios TV, as it cant get signal.
So, as a remedy, i thought it may be the HDMI cable and I just ordered 8k compatible cables ensuring that they do support HDCP 2.2. Will know tomorrow after I receive the new cables and how they perform.
if interested stay tuned...