1. Turn off data monitoring
Settings, Preferences, Data monitoring: off. It can quietly limit quality.
2. Free up storage
Settings, Applications, Manage installed applications. Clear the cache of your player and uninstall apps you never use. A full FireStick stutters.
3. Bigger buffer, right decoder
In your player: buffer Large, decoder Hardware. If the picture freezes while sound continues, try Software.
4. Fix the connection
A FireStick sits behind the TV, where Wi-Fi is weakest. An Ethernet adapter for the FireStick is cheap and fixes more buffering than any setting.
5. Restart weekly
Hold Select and Play for 5 seconds to restart.
Still buffering?
If every channel stutters only in the evening, it is your internet at peak time. If one channel stutters, try another version of it or tell your provider.