Susan closes the box that holds the Intercostal Clavicle, but when George retrieves the clavicle, the box is open ready for him.
When David and Susan first meet on the golf course, David is holding his club in one shot and then not in the next. The caddie behind also goes from holding a club and not in the same shots.
When Susan makes the long putt, she and David run side-by-side toward the hole. The scene cuts to more of a closeup, and Susan is suddenly 2-3 steps behind David.
When Huxley's caddie is walking along with Huxley and Susan Vance, his sweater is unbuttoned. On the next cut when Susan lines up her shot, the sweater is partially buttoned. Then on a following cut after that, the caddie's sweater is unbuttoned again.
When the dog is barking at Huxley, he is sitting in the center of a stair step. On the next cut, which is a three-shot of Huxley, Susan, and Aunt Elizabeth; Huxley is now sitting on the left corner of the step.
Susan says her brother trapped Baby while he was hunting in Brazil. There are no leopards (an African-Asian animal) in Brazil. There are, however, jaguars, which bear a passing resemblance to leopards. The animal shown is clearly a leopard (the telltale being the lack of dots in the center of each "rosette"), and correctly called such, even if the continent of origin is incorrectly named.
There is no such thing as an intercostal clavicle, since a clavicle is a shoulder bone and the word "intercostal" refers to a bone found between the ribs.
There is no glass in the windshield of David's car. When David and Susan are arguing over the ownership of the car and she drives off, to catch his balance David grabs the frame of the windshield putting his fingers through where the glass should be.
The dinosaur bone would have been too heavy for a small dog to pick up in its teeth and run quickly away. The bone more accurately would have been a fossil, with its organic material replaced by minerals. It would have likely had the weight of a large rock.
When George and Baby are wrestling in the woods, the big cat used is actually a jaguar. This kind of switch was common in film because jaguars are slightly more docile and easier to train. The substitution would have been advised, since the two animals were supposed to remain playful. A leopard would be much more likely to escalate the tussle to a full scale attack from instinct.
The Brontosaurus/Apatosaurus skeleton has numerous errors, including the head of a different dinosaur, Camarasaurus. This was not known until certain discoveries were made at least 30 years after the film came out.
Gogarty and Major Horace Applegate come across the leopard, and Applegate says, "Personally, Gogarty, I think you're a liar!" They start to run away from the leopard, when suddenly part of the leopard's head is transparent; one can see right through to the wall.
When Susan hits the back of the truck, the sounds of geese squawking can be heard, while it's chickens flying out of the containers.
When Susan is in her apartment and tells David she thinks he's "found a real friend" in Baby, a wire briefly falls into the view of the mirror in the background.
When Applegate and Gogarty find the leopard, the shadow of the leopard's trainer briefly comes into camera for a second as the leopard moves forward.
When Susan is dragging the wild leopard into the jail house, immediately after she utters the words, "Hey, David", an obviously mechanical stand-in for Baby (seated on top of the table) is seen turning its head.
When Susan follows Fritz into the house, the shadow of the boom mic can be seen against the wall of the house.
When David and Susan are putting Baby into the stall in the stable, the shadow of the boom can be seen in the lower front left corner of the screen as they close the stall door.
When Aunt Elizabeth first meets David at Susan's house and David tries to get everyone's attention by stomping his foot down on Susan's toe, the wide shot shows David breaking into a smile/laugh at Susan's reaction. The shot immediately changes to a closer angle with a more serious look on David's face, likely as a result of an edit to cover up Cary Grant breaking into a laugh.
(at around 1h 2 mins) David refers to "Major Appletree" instead of Major Applegate. This likely is an intentional "mistake" added for comedic effect.