When Shirley covers Ned with a towel, in one shot it is draped over both of his shoulders whereas in the other shots it's only over his right shoulder.
When Neddy arrives home, he puts his hands on his gate. Then he looks at his hands and sees they are red with rust which has covered the gate. A few moments later, it begins to rain and Neddy holds his hands palms up to the rain. His hands are clean; the rust isn't there.
When Shirley is wearing a pink bathrobe on the other side of the pool, she picks up a red folder and knocks some pens and pencils off the table and picks up one of two pencils still on the table. When she gets up and leaves, there are more pencils on the table than in the previous shot.
When Ned walks up to the boy selling lemonade his hands are by his sides but in the next shot they are on his hips.
At the Biswangers, when he is pushed, Ned's positioning in the close-up does not match the other shots.
When Ned and Julie are walking through the field, they both comment on the flowers visible, calling them marigolds and stating they usually aren't in bloom at that time of year. The flowers are Black-eyed Susans (Rudbeckia), not marigolds. If they were marigolds, in Connecticut they would be in bloom during the summer and early fall just as the Black-eyed Susans.
In the second shot of Ned pounding on the door of the empty house, the film is being run backwards - it's the same shot as before the interior of the house is seen through the broken window.
Ned arrives at the Westerhazy pool, swims three laps, jumps out and talks to Mr. Westerhazy. All this in front of Mrs. Westerhazy, and she acts surprised to see him.
When Ned is crossing the highway, bystanders can be seen on an on ramp.
Shadow of the camera and light-rig clearly visible at the first pool party on the backs of Ned and Julie as it swings around behind them.
When Ned is home, the tennis courts have tire tracks across them.
At the pool scene with Lancaster and Janice Rule, a camera shot shows a palm tree in the backyard. Palm trees can't survive in the climate of Connecticut, where the film allegedly was filmed in its entirety. Perhaps when the scene was re-shot with Rule replacing Loden, location shooting had already wrapped.