I’m not sure any of us really understand why force-quitting the Zwift app ‘fixes’ a number of issues, but it does. And Zwift doesn’t seem to be in any rush to remedy the situation (as it’s been this way for years), so it’s just a good habit to get into. (Do the same on your phone or tablet if you ever run Zwift on one of those, too.)
it’s sort of the Zwift version of ‘Have you tried restarting it?’
This is the oldest and slowest Apple TV device that works with Zwift, only 2GB RAM. Frequent quit and restart of the app is especially important on a device that old.