@NathanCooper assuming other devices are behaving normally the most likely issue is a poor WiFi connection to the device you are streaming through. You can check the speed most strreaming devices connect at by running the useful Network test in the Netflix's app Get Help menu. Streaming video requires a good stable connection so if the wifi is in any way dodgy you will get buffering.
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65inch Sky Glass, 3 Sky Streaming Pucks, Sky Ultrafast + and Sky SR213(white Wifi Max hub) main Wifi from 3 TP-Link Deco M4 units in access point mode
