I've been dealing with this EXACT same issue for around a year. And until now I was unable to find anyone online running into this bug. Interestingly, it seems that all of you have been experiencing this for as long as I have.
It happens in any app that shrinks the video into a smaller window while other content fills the screen. (I've seen it happen on Max, Crunchyroll, and DirecTV Stream).
A few months ago, DirecTV Stream updated their app with a home page that features a small windowed video playing the currently selected channel. When the bug happens, the only ways to get the video work is to either select a new channel using the guide, or use the left or right arrow to change the channel. Using the home menu gives you a black screen with sound. The top of the home menu shows a selection of recent channels, and scrolling through these brings the video back on the small screen, but making the video full screen through the home menu will still give you a black screen with sound.
As others have said, the only way to fix it temporarily is to reboot the TV using the settings menu. But the bug will happen again within a couple days. This has to be either a Roku or TCL issue, as it happens in several apps, and is not a problem when I stream content through my PS5.