One of the Black BT Wifi Discs https://www.bt.com/broadband/complete-wifi , the one closest to me during the day seems to have acquired a poltergeist. It's happened before, but now is more evident.
There is significant clicking (which does happen during a re-boot) but in the morning, the Disc has twisted slightly to its side, the result of hardware movement inside the unit.
Solved! Go to Solution.