Your upload speed is about 4 times slower than your download speed. if another device is using the internet then you or more or less half your speed striaght away. so in all your box will take longer to send the code to the server, and the receive time back will be slower.
This ends with your tv freezing. The code sent from your box to the server and then the server to send it back to your box as to be all done within 8 seconds and that is hopefully if the code sent was a good code, as sky send out bad codes too to create us problems that means the box will have to resend and receive.
Its not always the server to blame. there or lots of other factors that have to be right too. Internet speed, connection, ping and SNR. They all have to be good for the system to work perfectly, but its not a perfect world thats why its cheap. But sky is not perfect either.