The back of the handle was filled with black spots. I always stood it up rather than lay it down (which I think helped drain water).

The battery cover (tailpiece?) was cracked on mine after a year or so as well. It cracked in the back and water slowly leaked it (which I think did in the mechanism). I considered electro tape to seal it.

Reading the instructions on the new brush they specifically say to clean out around the lip of the tailpiece and the bottom of the handle when changing batteries. The fit is watertight so the calcium buildup must be just enough to crack it.

I hope this helps.

I never realized my emotional attachment to a silly brush until I took it apart and meditated I had the brush a year before I even met my wife… before three kids…. before the military.

It’s amazing how little things with small daily impact are magnified by time.

Anyway happy brushing!