The batteries need to have a full charge if they don’t you will get the 72. Even if it still reads close to but still under it can throw that fault. You should be able to run on inspection even with the batteries dead just won’t run on normal till they’re replaced. How many snow flakes come up when you try to run? If you changed the drive I would change the encoder or maybe do a learn trip and see if the problem goes away. Learn trip is a 116
