As I said, I saw them going in and out multiple times and when I walked by I even heard the flush. If it became faulty and as a result they locked it, what was the point of them cleaning up? Nothing to clean up because nobody was supposed to be using it. They certainly didn't look like fixing it because every time they went in, they came out within a few mins and the same crews had been using it throughout the flight. I also don't think this lavatory had to be locked because it was open to passengers initially and on another leg the same lavatory on the upper deck was unlocked.