The Case of the Hesitant Hostess - S1-E29
Factual error: Supposedly, heroin is being smuggled into the country in secret compartments in women's purses, but the quantity of heroin that could be concealed in such a way would be so small as to be very unprofitable for the smugglers.
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.