Flashing blue light on charge rather than the usual circle showing progress

I assume it’s buggered? Using a charger and cable i’ve previously used. to be honest i’m fuming that the doorbell has a built in battery since i’ve got a whole bunch of spare batteries from my previous ring 1/2/3 units I’ve owned. Wish there was a way to return and buy one that has the replaceable battery instead of having to unscrew the whole thing from the door every few weeks!