Arthur Ravenscroft wrote:

It went bang twice

All of the socket plates are not yet screwed down
and I've just retested it after twisting it a bit further away and now both sockets show 3 lights from the tester.

You need to check for loose or trapped wires behind the double socket
that went bang.

Yes, ensure there is no bare copper showing where the wires enter the
terminals, the earth wire must be sleeved, a short length sleeved
copper wire must be run from the earth terminal of the socket to the
earth lug on the back box, and try to get all the wires neatly dressed
away from each other as you fit the socket to the box.

--
Graham.

%Profound_observation%