In the swimming pool at the hotel, Lulu is naked in the long shot, but when she goes to talk to Ben, she wears a top.
When the bartender hands Ben the script, his pen is inside it. But when Ben takes it from him, the pen is attached to the cover.
Items on the bar move around between shots. There is a wine glass on the bar next to Ben that isn't there when he sits down or stands up. And there's a large napkin/straw/coaster holder that is at the far end of the bar when Ben comes in, moves right next to him when he sits down, and disappears when he stands up, all without the chance for the bartender to move it.
When Ben and Lulu are looking at each other after Lulu has shown her boarding pass at the airport, the same blonde woman with a red jacket walks by her twice.
When confronting the old man at The Pines Cafe, Lulu is wearing a striped tank top. But in one of the shots of the old man and Lulu's arm she's wearing a blue t-shirt.
While in a park near midday, Ben has two distinct shadows. This occurs when Ben is walking down the path to get his cell phone back from Lulu. The shadow from the sun is seen to his left and the other shadow is on his right, seen against some greenery and a tree. Possibly from extra lighting behind the camera.
Yellow tape is visible at the foot of the bed as Lulu is hugging the pillow after she finds out that Claire and Ben once had a child.