Did it clear tissues or maintain them as it should have for a battery change? As others have said, it sounds to me like there must have been a momentary power interrupt, probably because of a battery contact pressure issue. I've seen it happen on pre-battery compartment fix Predators, but never on my Petrel.
It maintained the tissues and deco schedule as well as a flashing red warning around the deco stop depth and time, everything else such as dive time and depth cleared.