Just tested it and it is fine. Other people haven't reported anything in that area either. Have you tried reloading?
Viewing post in Bug in Nao Stealth Mission (floor 7) making it impossible
I've tried reloading it a couple times from different saves. On my way back from retrieving the item (when Nao collapses and movement is slowed), I can pass through the door after the first chessboard, but not the second. I have tried everything I can think of, but it's acting as if it's just a wall. I noticed this glitch in the blacksmith's building on the same mission as well. I was unable to exit the room after looting it, and I had to restore from one of my previous saves. Is there any way to get around this one room? If I'm the only one having this problem, I would be fine with just using a cheat or something to bypass this.