@MicheleW the most common cause of buffering is down to poor wifi connection between the router and the device that is managing the stream. It is critical that video streaming device has a good steady wifi connection. Some customers report that Sky hubs have less range tgan the system they replace often that can be down to position of the hub has changed or they had boosters before and none now but overall it does seem some BThubs do have better WiFi range.
Sky sell an addon called WiFi Max which can supply up to 3 extenders which should sort this for you (see https://www.sky.com/help/articles/sky-wifi-max) It maybe worth calling Sky reporting the issue to see if they can cut you a deal on that package if the performance of the Sky hub is that much worse than the BT kit you had before.
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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
