Mine is doing the same thing.
Still has original batteries in it.
Going Friday to buy two Optimas.

I have a Surefire battery charger always plugged in along with a cell phone adapter. I don't leave a battery sitting in the charger and only use the CP charger when I need it.

I might try unplugging these to see if that helps.

3 years on the factory set isn't bad.....is it?