Ms Langer was seen on the elevator going elsewhere but then Frasier installs the door knocker and it was immediately tagged with the notification. Even if it was done by someone who worked for her that person would have had to be hanging out in Frasier's hallway.
Frasier is seen picking up the first two of his Polaroid photos from in front of the Condo Board members from his left to right. The camera angle changes & he is then shown picking up the second (for the second time) and third photos from in front of the board members. However, there were no photos in front of the far right board member to be picked up based on what was seen when he picked up the first two photos initially.
Just prior to attending his looming condo election, Frasier shows Daphne the "anonymous" letter that was placed on his car's windshield. After folding the letter back up, Frasier starts to put it inside his jacket pocket but pauses, with the letter mostly visible outside of his jacket. When the camera angle quickly changes, the letter is instantly concealed under his jacket.