I got my copy of the Chambers Dictionary from Books on Board (BoB).
I initially reported it's behaviour as a fault to BoB, but (after reading the posts here) told them it appeared to be a CyBook issue, and I was happy for my fault report with them to be closed.
They acknowledged that, but have subsequently sent an email saying they're still looking into it, and requesting the build details for my CyBook.
I must say, I'm very impressed with BoB's perseverance

- if I get any feedback from them I'll post an update.