The bike that Renato rides, suddenly has a modern derailleur-type chain tensioner at the rear at about 20-21 minutes into the film. At all other times, his bike has a fixed rear gear without the chain tensioner.
Renato's bike changes position when he helps Malena pick up oranges.
When Malèna is hit by the local women after becoming a whore and her hair is cut, she doesn't have any marks or cuts on her head. But later there are sometimes two spots or cuts on her head.
When he is peeping Malena first time at her apartment, Its night time outside. But inside its definitely daylight all around.
After Renato passes out, he is in his mother's lap. His arm position changes between shots.