The report discusses various factors, snapback areas, toolbox meeting master pilot exchange and so forth, the most blatant violation is using the main engine during a line-shift while alongside. They had two tugs.
At 0832:42, Mona Manx’s engine control was set to dead slow
astern, and the vessel began to move astern, eventually reaching a speed of 0.5 knots. During the manoeuvre, the forward mooring party heaved in the slack on the forward spring and the aft deck mooring party slackened down the aft spring
At 0836:31, a linesman on the quay was moving forward towards the tensioned spring line when a loud bang was heard as the line suddenly released and recoiled vertically upwards (Figure 7). The linesman quickly moved away but the spring line struck the 2/O under his chin and he was lifted off his feet and thrown backwards,
causing his head to strike the accommodation ladder that was behind and above him. The force of the impact threw his safety helmet backwards, and his VHF radio was catapulted into the water as he collapsed onto the deck.