erratic implementation of TOC settings

Hello
this is a great module and it is a shame it has been marked abandoned for political reasons...
i am having an issue with it in that some books are working fine and displaying a TOC down to the level I tell it to, others display no TOC in the sub-pages. I have compared the settings on the pages which differ in this way and the settings are the same!
any ideas? is anyone still working on this project?
cheers

book example: http://gpstsociety.org.uk/training-resources/