From the link you posted (the main thrust seems to be around using extension leads of insufficient cross section conductors, some talking of just 1.5mm!)
"As sockets age the contacts can loosen, meaning that the contact between the socket and plug pins is not as firm as it should be, which may increase the risk of over heating. We would always recommend charging your EV from a relatively new branded socket, such as one manufactured by MK, Crabtree, Schneider, Hamilton etc. "
The other socket in the image also shows early signs of overheating, suggesting an inferior product? A properly installed ring main with cable of 2.5mm conductors will handle the typical 10amps without issue
As with anything electrical, get expert support and have the installation checked by a professional