Other mistake: When Oliver is meeting Fagin and his boys, he says, "Is this a laundry then, sir?" You can see Jack Wild (Dodger) mouthing that line on the left side of the screen.
Other mistake: When Professor Potts bought Chitty from the Junkman and brings the car into the garage, the body of the car is charred or damaged somehow from the crash and fire. But the leather seats, dashboard and wooden steering wheel are completely unharmed.