Electric pepper mill - not working? (SG4 hitchin)

We bought one of these about a month ago, then it just stopped working, we got a replacement, then the first one started working again. Then it stopped working and the other one worked but stopped working. Not sure if there is a loose connection inside or something but if anyone wants to try fixing one or both, they were good pepper grinders before they stopped working! Takes 4 AAA batteries.