Just before Hobart proposes to Bea, he shows her a box full of old memorabilia that had been buried for years. The box is a Converse sneaker box of a newer sort with an attached lid. In the time frame the lost box was first buried, it would most likely have been different, with a detachable lid.
When Beezus is upset because she just spit all over Harry after drinking a lemonade with a fly in it, Beezus is on stomach on her bed upset. She looks at Ramona and she has hoop earrings in, then the camera goes to Ramona, and back at Beezus and she doesn't have the earrings on anymore.
When Ramona and Susan are talking in the music room, Ramona's top button goes from done to undone and back and forth a few more times. By the end of the conversation it has been undone for a few shots in a row, but when she gets up and goes to the window it is done again.
In the scene where Beezus and Hobart are dropping Ramona off at school, a piece of Aunt Bea's hair is sticking out to the side. The camera turns to Ramona and when it comes back to Beezus, her hair is smoothed down. In the next shot of Aunt Bea, it is again sticking out.
The goof item below may give away important plot points.
Mr Quimby cuts the burrs out of Ramona's hair, creating several short layers on top. At Beezus and Hobart's wedding, which was planned in three days, Ramona's hair is back to all one long length. At the wedding Mr Quimby also mentions the phone call from Mrs Meacham was "a couple days ago," so enough time has not passed for Ramona's hair to grow back out.