Continuity mistake: In the scene were Gilbert and his friends are in the diner and Gilbert is pouring the salt out onto the table look at how much salt is in the bottle just before the shot switches to Gilberts friends and the look at how much salt in the bottle when the shot switches back. In the first shot there is less salt than in the second shot.
Continuity mistake: In the sunset scene, Becky comments on how Gilbert missed the sunset. Then later, stock footage is used to show his house, and we see that the sunset is still going on. Not only that, but Gilbert's house consists of a single building, while this shot shows more than one building.
Continuity mistake: In the scene after the funeral, you see that Juliette Lewis gets groceries and gets a ride from Johnny Depp. They put the groceries in the back of his truck on the right side under a tarp because it's raining. When they get to her camper, the groceries are now on the left side of the truck.
Revealing mistake: During the rainstorm, after Gilbert delivers Becky and her groceries back to the camper, they are embracing in the rain and hoping that Nana won't get the camper started. You can see sunlight reflecting off the truck, their hair and their shoulders, even though they are standing in a supposed downpour with a completely cloudy sky.