When Duffy comes over to Mae and Sadie's hotel room to open a bottle of beer; he ends up spraying beer on Mae's dress and staining it. But on the very next cut when Mae goes to check on Deacon, her dress is now clean and stain free.
When the girls arrive in Havana, Glenda's scarf/collar keeps changing the way it is draped, buttoned over the left, and buttoned over the right, back and forth, several times.
The Hotel bill sent to Sadie reads "El Havana Hotel" but this is wrong. In Spanish, Havana is spelled Habana. The proper grammar and spelling in Spanish would be Hotel La Habana.
When Duffy is in the telephone booth talking to Sadie; his hand brushes against the mouthpiece causing it to shake. This indicates that the phone was a rubber prop.