They are physical contacts. They get dirty. They wear. And if wear and dirt/dust combine and two internal contacts are closed with a single press, you'll get what you are experiencing.
If that is the remote that came with the device, it's six to seven years old, as the Roku 4 was in production from 2015 to 2016. And the remote is the most physically used part of a Roku setup.
If dirt/dust is contributing to it, then blowing it out with air -- compressed air cans may be useful, the same ones that can be used to clean a computer keyboard -- may help. If it's wear, there's not much to be done.
If a replacement is in order, any of the Voice Remotes ($20-$30, available at Walmart, Best Buy, many other retailers) will work on it, or any eventual Roku replacement device.
Roku Community Streaming Expert
Note: I am not a Roku employee.
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