When Lena is packing to go back home and she drops her paint brushes, when she bends down to pick them up and sees Bee's letter under the bed, she picks up the brushes with her left hand but places them on the floor and gets up. In the next shot we see that she's still holding the brushes.
When they first are trying on the pants. Tibby is standing outside the changing door/sheet thing and there is no hook on the wall behind her. She closes the door and opens it quickly and a hook has appeared.
The movie indicates that the scene, where Tibby and Bailey are looking up at the stars and when Lena and Kostas are out on the boat, are around the same time. But Maryland and Greece are in very different time zones, eight hours apart. However, it could be 10-11 at night in one place and 4-5 in the morning in the other place, so it would be dark in both places.
Throughout the movie, the color of the pants change. When Bailey holds them up and asks Tibby about them, the pants are light blue. Then when Bridget gets them, they are dark blue. And when Carmen wears them to go try on a dress for her dad's wedding, they are a medium blue. However, this could be part of the "magic" that adjusts the pants to each girl.
The goof items below may give away important plot points.
At the end of the film where the four girls are sitting at a round table at Carmen's fathers' wedding, the glasses of water are shown with different levels of fluid in them between shots. This is fine except that the last shot as the camera moves away show that the glasses have magically refilled themselves.
At the end of the film where the four girls are sitting at a round table at Carmen's fathers' wedding, there are bits of white lace tied to the back of the girls chairs. In one shot there is nothing on the back of Carmen's chair and in the next shot all four chairs have lace tied to them.