I was on our last 747 that we had in the fleet, going HNL-PHX.
We took off, and about 30 minutes later had to return, as the main gear doors wouldn't shut. Given the dodgy nature of our 747's it was a bit scary and we had a pretty rough landing. We all got off, got back on 3 hours later, sat for an hour, then they cancelled. I got home on another airline the next day, but the plane had the same problem the next night, and ended up spending 4 days down in HNL, and as it was our only 747 left, lots of cancellations.
Also, once flying into SAN I saw a large quantity of oil splattering on my window on final. It alarmed a few folks, myself included. Then I noticed that the oil didn't smear and that it dried. Turns out it was coffee, the FA poured it into the sink and it sprayed out all over the plane. I felt sorry for the pax in SAN going on the next flight, as the pilots and ground crew were all walking around the plane pointing out the black stains. 🙄