App-side buffering usually traces to a corrupted local cache or a bug introduced by a recent update, and it has nothing to do with your line or your router at all. It tends to show up right after you update the app, since a new build sometimes ships with a broken cache-handling routine, or it builds gradually as the cache fills with stale data over weeks of ordinary use. Clearing the app's cache and data is the fastest way to rule this layer out before you look anywhere else, and it costs you nothing but a couple of minutes. If clearing the cache doesn't help, that's useful information too, since it moves the problem firmly out of the app layer and into device, network, or server territory.

Player apps hold the entire visible channel list in memory the whole time they're open, and that load grows as your list grows, whether or not you ever watch most of those channels. Above roughly 18,000 visible channels, players start to destabilize just from carrying that list, which shows up as buffering on channel switches rather than during steady playback of a single stream. Hiding groups you don't watch is a real fix here, not a cosmetic one, because it directly reduces what the app has to hold and track at every moment it's running. Older or lower-memory devices feel this ceiling sooner than newer ones, so the same channel list can behave differently across two devices on the identical connection.

Network-side issues show up as a gap between what your resolution needs and what your connection can actually sustain over time, not just in a one-time speed test. 4K needs 15-25 Mbps sustained; 1080p needs 5-8 Mbps. If 4K buffers but 1080p doesn't on the same connection, that gap is the cause, not the app or your device, and no amount of cache-clearing changes it. Buffer and DNS settings help here too, since both affect how the app handles a marginal connection: a smaller buffer recovers faster from a brief dip, and a faster DNS resolver removes one more source of delay before the video even starts loading.

If a specific group of channels buffers for everyone watching it, not just you, the fault sits with the shared upstream feed on the provider's end, and it will show up the same way on a different device and a different network too. Nothing local fixes this, no matter how carefully you tune your buffer or your DNS. It's the reason a provider's published uptime figure matters as much as any setting you could change on your own device, since that number is the honest measure of how often this particular layer fails across the whole service, not just for you.