Return to factory wasn't really an option!This is a truly amazing story of fixing a nearly 50 years old computer
https://www.theguardian.com/science...n-after-nasa-remotely-fixes-46-year-old-probe
I’ve replaced several Oral-B batteries over the years. They seem to use a poor charging module and often all that is needed is to charge the battery in a proper charger once every month or so.Maybe you can replace a toothbrush battery? Will have to give it a go.
Tech Tip: How to repair your electric toothbrush
Most Oral B brushes can be opened by holding the toothbrush and the charging stand togetherwww.independent.co.uk
Now found this: