Rat 5
I do remember the story of a BA B757 on base training duty who could not get the gear down by any means. The solution devised (lucky they had the fuel while the tech gurus devised the solution) was to depressurise the hydraulic system which kept the gear up. Then the back up system could be used and once released aerodynamics + gravity did the rest.
You remember well. In fact story went that Gear Lever actually came off in hand during UP selection, so all gear pressurised up and solution as you posted. There was a procedure in the QRH for that for many years afterwards.
I was going to venture something along the same lines for this LOT incident but you beat me to it in a way. However I think it is possible that this incident will turn out to be gear still pressurised up as that would be the only common link. Perhaps the selector valve stuck/trapped in UP position? Cable snapped after UP selection? This would preclude Gravity procedure.
Just a couple of thoughts.