Shitty design. Doorbells should never need batteries. Even a tiny, tiny solar power panel and a method of power storage would be able to keep it going indefinitely.

Our door bell harvests the kinetic energy from being pressed and uses that to generate the trigger signal for the base-station. Sadly it fails if the push isn't firm enough, it appears not to have any sort of battery.

That works both ways. We have an actual bell as a doorbell. People knock because they don't realise they can ring the actual bell. -.-