I’m a retired container ship (and tanker) captain.
It was the wind.
There were no stairs involved.
What does stairs have to do with it (I don’t get it(?))?
I don’t believe any supposed “official” explanation by them, no matter how possible in other scenarios etc.
A close friend's sister was a steward with the Seafarer's Union who was murdered and her body found floating in the Chesapeake Bay back in 1993.
Her case was highlighted on the program Unsolved Mysteries and in 1997 the murderer was arrested while incarcerated in a Florida jail for an unrelated crime.
Apparently the guy bragged to a fellow inmate about the murder and the guy turned him in........