Buffering is a symptom, not a diagnosis, and it has four quite different causes. Changing settings at random occasionally fixes it and teaches you nothing. Twenty minutes of structured testing usually finds the actual problem, and three of the four causes have straightforward fixes.
First, narrow it down
Before changing anything, answer two questions. They eliminate most of the possibilities immediately.
Does it affect every channel, or only some? If other channels in the same category play perfectly, your device and your network are demonstrably capable, and the problem is the source. There is nothing to fix at your end; report the specific channels and times.
Does it happen on another device, on another network? Open the same channel in a player on your phone using mobile data rather than home Wi-Fi. If it is smooth there and stutters on the television, the problem is local. If it stutters on both, it is upstream.
Cause one: the source
Specific channels failing while others are fine is a source issue, and it is particularly common during popular live events when many people request the same stream simultaneously. No setting on your device changes this. Note which channel, what time, and whether it is consistent, and send that to your provider — specifics are what make it investigable.
Cause two: Wi-Fi
This is the most common cause of “everything buffers at home but not on mobile data”, and it is where most people should start.
Streaming sticks are the worst affected, because they sit behind the television — a slab of metal and glass between the aerial and the router. A short HDMI extension cable that moves the stick out from behind the set frequently fixes buffering outright, and costs very little.
Beyond that: use the 5 GHz band if your router offers one, since it is faster and much less congested than 2.4 GHz, though it carries less well through walls. If the device has an Ethernet port, or accepts an adapter, a cable removes the variable entirely. People are often surprised how much difference this makes on a connection that tests fine on a laptop in the same room.
Cause three: the device
A device at its processing limit stutters in a regular rhythm rather than pausing to rebuffer — picture a steady judder instead of a spinning loader. The giveaway is that it affects higher-quality streams while standard-definition ones are fine, even though your connection speed has not changed.
Two things to try. On Android-based players, switch the decoder setting between hardware and software: streams the hardware path rejects often play cleanly in software, at the cost of more processing. And close background apps, which on cheap sticks with very little memory makes a real difference.
If an older device judders on everything above standard definition, you have found a hardware limit. A current streaming stick is the cheap answer.
Cause four: the connection itself
Run a speed test on a device connected the same way the player is — testing on a laptop two metres from the router tells you nothing about a stick behind the television. Compare the result with what you need: roughly 10 to 15 Mbps per HD stream, 25 Mbps or more for higher resolutions, multiplied by the number of connections running at once.
Also watch for evening-only buffering. A connection that is fine at midday and poor at eight in the evening is a congestion problem, either in your household or in your provider’s local network, and no amount of player configuration will fix it.
What to send when you report it
Having worked through the above, you can describe the problem in a way that gets a real answer: the channels affected, whether others work, the device and app, whether it reproduces on another network, and your measured speed at the device. That is the difference between a reply that fixes it and a reply listing things you have already tried.