Smart TV operating systems run on more limited RAM and CPU than a dedicated streaming box, and at launch the app has to build its channel list and start pulling guide data while the TV's own system processes are still active in the background, competing for the same limited resources. That competition front-loads the delay into the first minute or so after opening the app, rather than spreading it evenly across the session. Give the app a little time before selecting a channel instead of backing out, and close any other apps left running on the TV, since background apps quietly hold onto memory the player app needs to build its list at launch.

The program guide, or EPG, loads on its own schedule, completely separate from the live channel stream, and TV apps often use a longer background refresh interval for it than phone or box apps typically do. That means the guide can lag well behind the channel itself already playing fine, which can look like a bigger problem than it is. Leave the guide open for a moment and let it populate on its own rather than backing out and reopening it repeatedly, which restarts the fetch from the beginning each time and actually makes the lag worse, not better.

This is a distinct, recurring cause worth checking on its own: a post-update regression. The TV's system software update changed something in how it allocates memory or handles rendering, and the streaming app on it hasn't been adjusted to match that change yet, even though nothing about your connection, your account, or the provider changed at all. Check whether an app update is already available that matches the new TV OS version, and reinstall the app if one hasn't been pushed yet, since a stale app build running against a newer OS is a common source of exactly this pattern.

That comparison isolates the fault to the TV specifically, since a different device on the exact same network and the same account loading normally at the same time rules out your connection and the provider as the cause entirely. If more than one player app is available for your TV, try an alternate one on the same source — different apps use different underlying playback engines, and one may simply run better on that TV's specific hardware and OS version than another does, for reasons that have nothing to do with your subscription.