Hi, thanks for message and the video! You have to close the door from the room where the note is, otherwise trap will be activated if you try to leave the downstairs. After you exit the downstairs, you no longer have to worry about closing any doors.
Next to the phone you will find a note which has following line "Keep staff areas secure by closing door when not in use, failure to comply with the policy will result to fatal disciplinary action being taken." I do apologize if some of the messages/notes are not clear enough. As english is not my native language, game might contain quite many typos and hard to read text content.