Had this happen during a run, somehow clipped up onto the top deck and AI wasn't loaded (they weren't shooting at me). I tried to replicate it but couldn't, thought I'd post anyway.

This would save a little time climbing the ladder and also avoid getting killed if it was consistent.

I cant tell You how this is done ether. But it hase something to do with the rolling. I found the same glitch in Black Monday where it teleports you to the floor on top when You roll against a specific wall in a specific spot in the first mission.