When Mad Maggie bites the suitcase, some sticks and debris appear on her head. A few seconds later, they disappear without any movement of her head.
When the girls show up at the Rod and Gun Club, Joe and Gus are seated with wine on the table. When they stand up to greet the girls, the wine disappears. It reappears after they sit again.
When Joe and Gus are at the entrance to the cave they are using an led penlight style flashlight... After they enter the cave it switches to a full sized standard flashlight.
When the two girls drive up to Joe and Gus as they are pushing their boat with trailer on the highway, the girls' El Camino has no trailer hitch. A short time later, they are towing the boat on its trailer.
In the final scene, Joe and Gus are back in New Jersey and encounter the same alligator that they did in Florida. This is not likely because North Carolina is as far north as alligators live.
When Joe and Gus are watching "Jeopardy!," there are watching it on channel 3, but when Joe changes the channel to watch "Country's Criminals," the TV still says channel 3 when "Country's Criminals" should be on another channel.
One of the final scenes shows a "media frenzy." A lens enters from the left of frame, but instead of being a prop TV camera, it's a Panavision Primo lens from a 35mm film camera used to shoot the movie.
When the knife falls of the boat (at 0:44:10 to 0:44:19), it has a wire visible dangling it from to the boat.
When Gus and Joe find the treasure map in the back of the Barracuda, Gus says "Just like he said," while talking about the reward. But it's not a he, it is the lady from This Country's Criminals.