Similar happened to old APL Belgium in OAK years ago. Stack fell onshore; terminal tractor trailer got lucky by about 10 seconds. As previously stated, if you unlash/unlock everything and then discharge all the way down one cell trying to get a hatch cover off (because the gantry driver is just following orders), leaving an adjacent tall cell unlashed, let alone multiple…. avalanche by a single good bump is possible. Too much list to one side due to inadequate (or often broken) anti-heeling system capabilities COUPLED with (at times) 4-7 cranes all discharging from the same direction can make this happen even more easily.
Every now and then this happens even to lashed boxes if crane is a little careless and hits an unlashed / unlocked stack with a hatch. I would say losing containers alongside in the port is 9 times out of 10 due to gantry operators. And it’s a few boxes, NOT avalanches like this.
However, 2 different bays dozens of meters apart is a catastrophic CF. Good grief.