This thread has gone dead, so I don’t think anyone is likely to respond now, but I thought I’d give an update.
Had an engineer out today. The issue appears to be due to a broken wire in the door itself. It seems that the bundle that crosses at the hinge has failed due to constant movement at some stage, and the only solution is a replacement door, because it’s a sealed unit and the wiring is inaccessible.
I did find another thread online describing the exact same issue with a different model LG fridge freezer from 2019. Their repair also required a door replacement.
So, if anyone is reading this, and sees a similar issue in the future, then they might find this info helpful.