Regarding walls and magnets
We too were on this cruise and disembarked in Athens (which, by the way, was the fastest we have ever experienced – 15 minutes from cabin to exit!).
We were also in a PH and, finally, at the end of the cruise (an how was that helpful 🙄?), I tested the walls with some magnets. All the walls accepted magnets, except the wall with the mirror, desk and fridge. As well, the wall above the bed is covered with a lattice and also won't accept magnets.