The problem has came back, several days ago. I think I have identified the cause.
Each time I launch my Cube the Keyboard etc disconnects a few seconds after signing in, and is unusable. I have tracked this down to an issue with the Pogo magnetic / USB dock. It is repeatedly becoming disconnected to the Board. I have confirmed this by briefly removing / returning the Board to the dock, after which the devices work for seconds (enough to sign in), then stop working. Furthermore, I now have a second compatible Pogo Keyboard, similar in layout to the Cube’s original Keyboard but without the USB ports which works alright, proving there is not a problem with the computer itself.
I have cleaned any dust away from the attachment points and cannot think of anything else to try. Are there any suggestions of what else I can do, apart from returning it to BangG for repair / replacement?