Oh, here you gave me the impression you were running 2s. May have run it to low, or possibly didn't have both packs fully charged which can run the low pack wonky. Also as your packs get a lot of runs on them they can become mismatched which can run one of them wonky. I like to test all my cells periodically with a voltage tester before, after charging, and after running to know for sure where they are at.