As Perry and Della enter the elevator at the Holliday Arms, it is clearly not an elevator. There is no shaft opening or door tracks visible.
As Perry and Della are preparing to leave for Holliday Arms to see Patton, Perry tells Della they will need the briefcase that Bradbury left with information on Patton. However, Bradbury gave them a manila folder, not a briefcase.
Thelma tells Perry that George Sanborne lives in the El Vista Apartments, but the transition shot shows footage of a hotel, not an apartment house.
When Perry and Della open the elevator it is clear it is stage dressing. There is no seam on the floor both getting in as well as out.
The character played by Jeanne Cooper is called Thelma Bell throughout this episode, but in the credits she is listed as Thelma Hill.
The character played by Doreen Lang is clearly referred to as Miss Fields, but in the credits she is listed as Mrs. Fields.