There were 2 maps missing some stairs. Other players could walk the stairs but for me even the collisions were missing.
Unfortunately I don’t know the name of the first one, it was a ruined library with spiral staircases upwards. Other times on this map I saw the steps and walked them.
The second one was the final steps to the eternity last fight.
Interestingly when I jumped on the nonexisting steps my hero fell and was hanging from the invisible steps.
I verified my files of course, nothing is missing.