My daughter’s Sonicare Pro Electric toothbrush broke. It doesn’t vibrate any more. I googled around and saw the Lithium Ion battery may be the culprit. So I opened it up to look around. I verified that the battery is registering 4.0V, which is still fine. When I bent the stem a bit, the toothbrush started vibrating again. I determined that there must be a broken trace on the printer circuit board (PCB) probably induced by the vibration or a kid’s abuse. I decided that it’s not worth my trouble to revive the unit. It was difficult to repair as along the way, I broke the inductive wire connected to charge the battery. My decision – discard/recycle it. It not worth the trouble. It may be a fun project to root cause the problem but not for me. I have better things to do. It costs ~$60 to purchase a new one.