The speed of your connection does not matter as much as the routes your provider uses. You can have a gigabit connection but if your provider routes your connection to Europe through the US you're going to have a bad time streaming. That's why VPN helps. Using different VPN servers gives you different routes. If your route is already good VPN adds more overhead and makes it worse though, so it's only good to use when you need it.
[XX='IanTheExplorer, c: 870004, m: 732441'][/XX] Try the NBA 1-17 channels instead they are from a different source. If it buffers use European VPN. I had trouble finding a good source for ESPN lately that will not buffer.
[XX='IanTheExplorer, c: 870048, m: 732441'][/XX] I changed the source of ESPN now too, if you restart Kodi you will get the other one instead. If there's buffering use US VPN.