I think it is repairable. This grey cylinder has magnet attached on top and some plastic inside. It connects to a metal head on the end of motor shaft. My understanding is that plastic was glued to the metal head, but after short time connection fails. Which is very disappointing by Braun, indeed. I was able to disassemble my brush, using minimum tools and photos on this site. After understanding how it works I glued "grey cylinder" back to the metal head on the end of the shaft. Used super glue (cyanoacrylate) with baking soda as a glue, simply because that's what I had. Applied some extra amount of glue mixture so it forms a cone on the end of "grey cylinder" for better connection. Works so far. 🤞 UPDATE: After about two years it still works. So it is repairable.