I've used this design before and I know the duplicants were able to pass through this door to get from the upper chamber to the lower one. I now noticed that when the door is buit, even if it is open, it prevents duplicants from passing. Is this on purpose or is it a bug?
No door, they can pass:
Add a door, they can not (door set to "open" - which wasn't needed before):
Steps to Reproduce
Build door like in pictures above. It blocks the lower room from the upper one.
This issue has not been confirmed by a developer yet.