Check the age of your chargers on the bottom. Personally a few of my chargers went bad from the 12V platform. Those were older ones from 2007-2010 so it’s understandable. Like other I have old 1.5 batteries that are a decade old, they all still hold a charge. My 2.0’s have been in much heavier use with the FLA12’s sometimes running 10 hours or more a day, sometimes that might mean the battery needs a cool down period for best charging.
The master has failed more times than the disciple has ever tried.