Wouldn't surprise me if it's software ( I don't have inside knowledge of Cs) , as often when some trains like multiple units attach or detach the train management software melts down and won't recognise the new formation or some other issue . Simple mechanical couplings, air pipes and jumpers just need a person to put them together right, not permission from a computer as well
However, due to the substantial PR damage that CS must be getting and possibly a loss of repeat business, I'd have thought that a fitter was in attendance at every split or join or even on board all night. I don't know however.
Additionally, the need to start the depot prep work a couple of hours earlier each evening to make sure they beta RT departure from depots so that people aren't left hanging around on platforms late at night....