I don't think there's any feature there with the video jumping back. That purely seems to be a bug where it fails to resume the connection to the server to continue filling the buffer. It seems to hit the end of what is buffered and then refresh, causing it to jump back to some last saved position.
This doesn’t explain why it does that after you jump elsewhere, why it does that only after several hours and why it started recently. This “some last saved position” doesn’t persist when you refresh and is always exactly -20s from where you paused. It’s not a single event I got my observations from.
