It's been a few years, but for anyone that comes across this post, in answer to Jon Jensen's post, I discovered that there are two tabs that have to be released to allow the central shaft to be pushed out. The tabs are accessible from the bottom of the toothbrush after removing the bottom cover. They're hard to access and must be pressed inward. I discovered this AFTER breaking open my case and seeing why the shaft wouldn't come out. Hopefully this helps someone else.