Not exactly the same situation, but I once had a 5-day, 2-hour long rental where the computer was trying to charge the weekly rate plus two additional hours.

The agent extended it a few hours to kick it back to the weekly rate, but when I returned the car the rate reverted back to the original problem of extra hour charges. They fixed it inside without a hassle, but just a heads up that the rate might revert when you return the car.