Test the actual television
Use the television or streaming device you plan to keep using. A phone beside the router may have a very different Wi-Fi signal. Compare Ethernet where supported to isolate wireless coverage from the service itself.
Watch the household load
Pause large downloads for a comparison and note whether other screens are streaming. Try a lower supported resolution and observe whether the problem changes. Your purchased simultaneous-screen limit also needs to match active playback.
Record a useful result
Write down the player, device, local time, affected channel and whether another live stream or on-demand title works. These details help support distinguish an app issue, local congestion and a source-specific problem. A successful short test is useful evidence, not a guarantee of every future session.