I assume you're speaking of YoutubeTV. It would really help if people would state what app they're using as "previous channel" is meaningless in something like Netflix.
It's a YoutubeTV thing. Does it follow the remote or the Roku device? You'll find a few threads about it. You can contact Youtube/Google and ask them or wait for the full rollout if they decide to keep that feature. It's not really a Roku issue.
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