As Pop is proposing the con on the widow to Nick and Al, the same couple (a blonde and a man in a vertically striped robe) walks past the window along the beach from right to left twice.
The amount of foam and beer in Pop's mug changes as Doc tries to get information on Nick from him at the dive bar.
The moonlight is shimmering on the ocean while Nick and Gladys are in the restaurant. Gladys even comments that the Moon is just coming up. A few minutes later, the sky and ocean are as completely dark as they would be on a moonless night.
The sound of the riffling cards does not match with the riffling that Doc is doing in the shack. In addition, one last riffling sound can be heard as he is setting the deck down on the table.
After Nick ties his tie, he and Al walk into another room. A shadow of the boom microphone can be seen on the wall to the left of the doorway.