Tony dives deep to find the girl in cement, but the shot of her from the ocean floor shows she's only a few feet underwater.
During the car chase, there are multiple instances where the scenery visible from the inside of the cars does not match the scenery in the long shots outside the cars.
When Rome goes into the back room of Jilly's, he goes through a glass door with sign writing on it and opens the door with his right hand. The shot as he enters the room shows him opening the door with his left hand, and the door is now made of wood and has no sign writing.
When Kit is making hamburgers at the bowling alley, she is holding an empty plastic bag. At one point, there is a hamburger already in it. Then, the next scene of her shows her putting in the hamburger she was preparing into an empty bag.
Arnie's model's scarf changes from pink to yellow/orange between shots.
A local TV station would never break into the broadcast of a national program (especially one like Daniel Boone (1964), aimed at children and families) to announce the murder of the owner of a two-bit go-go club.
When Waldo Gronsky smashes the cop's head in to the closed window on the police car, it shatters like plate glass. Real auto glass would bead when broken.
When Tony calls in the discovery of the lady in cement, he says, "over and out". He should have just said, "out". "Over" means the transmission is finished and awaiting a reply. 'Out' means, transmission is finished and no further reply is expected.
The coroner states that the lady in cement was killed by a stab wound under the left breast bone into the heart. However, despite several long lingering looks at the corpse, no stab wound is visible.
(at around 1h 4 mins) When Lt. Dave Santini kisses his son, he's wearing the wedding band on the wrong finger; it's on his pinky finger.