Thank you for your help – I have found the offending function.
The plugin is meant to manage about 400,000 case files and provide a fast search. In order to manage the search on the front-end of the site, I need to manipulate the number of results found for any given search, so I added a filter at “found_posts” to do that, and that was breaking the pagination on the backend.
I added “if(is_admin()) return;” to that function and everything is hunky dory.
If you are interested in seeing a fast search in action, look for “dismissal” or something on http://dev.caselaw.co.za/search-page/