Continuity mistake: When Nino goes to 'Les deux Moulins' for the first time, we can see Amelie writing the menu on a glass right behind him. A few shots later, we see the glass again and the handwriting is quite different. That's easy to see if you look carefully at the 'd'. Later on, we see the glass once more, and the handwriting has changed again.
Continuity mistake: Before Dominique Bredoteau enters the phonebooth he has a bag in his left hand. When the camera angle changes he transfers it to his right hand as his arms suggest. When he replaces the handset he swaps the bag back to his left hand picking up the tin box with one hand. The camera cuts to an overhead shot of him holding the tin box with both hands not allowing enough time for him to put the bag down.
Continuity mistake: When Nino pulls back the photo booth curtain to reveal the bald "mystery man", the man's toolbox is on the photo booth stool. However, shortly before, we saw the legs and feet of the man standing in the photo booth, and the toolbox was nowhere in sight, and there was nowhere in the booth to hide it.