Hi Scott,

Firstly, may I know are you referring to built in EasyDiscuss search or Smart Search module. I believe you are referring this with the Smart search module yes?

For your information that EasyDiscuss category can set to multiple Joomla user group which is in the finder_links table access column it only can be inserted single Joomla user group access
There will be conflict if each category have multiple Joomla group user access.
However, I've inspected that in your site, you only set single/one Joomla group user can be access for each category which is possible to make a quick hack for that. Can you download the attached file and replace it in the folder:
.../plugins/finder/easydiscuss/easydiscuss.php
then clear and re-index back the smart search

You're suggested to backup the file that you want to replace beforehand for precaution