Citadel of Eternity Vanishing Stairs.

I was playing Chaos Wastes with a friend who has never done the DLC before,
We finally got to the final section of the run, when my friend playing Waystalker said they saw an optical illusion (or a visual bug) of one of the skulls floating in the air.

I went to approach the stairs walking backwards so I can see what they were talking about when I fell off without warning.

I understand the stairs may have been removed to prevent the players from running away, but there was no warning for this to happen.

It left a bad taste in my friend’s mouth who just went off for the evening, annoyed with how the run ended.