Buffering or stuttering

The picture plays, then stops to buffer, then plays again.

1. Does it happen on every channel, or one?

One channel. That stream is being delivered slowly by your source. Nothing on your side will change it.

Every channel, all the time. Something between your device and your source cannot keep up. Continue below.

2. Is anything else using the connection heavily?

Another device streaming, a large download, or a backup running will starve playback. Pause them and try again. If that fixes it, the connection is the constraint rather than the app or the source.

Recording while watching counts here too: both are separate streams from your source, and some sources limit how many you may open.

3. Is it worse on Wi-Fi than wired?

If a wired connection is noticeably better, the problem is local reception rather than your source. Moving closer to the router or using 5 GHz usually resolves it.

If wired is no better and one source buffers while another does not, the difference is the source. The app plays both the same way.