OK, this one is baffling. It’s a fireproof (well, more likely, just fire-retardant) door between a lounge and an equipment / elevator room.
It looks like they made the door by casting something like concrete inside a standard lauan hollow-core door.
What’s truly odd is that the concrete (or whatever) filling is also warped, convex side outward. The door edge strip with the latch is straight as an arrow, having separated from both of the facing panels and the concrete core at the bottom.
Did the outside of the door get wet in some way that didn’t soak the surrounding room?
We’ll never know…