The Case of the Wayward Wife - S3-E13
Revealing mistake: Perry and Della step into an elevator but there is no line in the floor between the floor they are on and the elevator floor. It's continuous.
The Case of the Wayward Wife - S3-E13
Factual error: May buys a book for 4.95. Give the clerk a $10 bill but the register shows change of $5.15.