Hi nomadicfrog,
I'm sorry for this late reply, when any thread got replied it goes to the top of the list in the forum, so posting many replies will keep pushing it away, that's why WP forum moderators recommend "No_Bumping".
Regarding your question, could you please disable all your other plugins -temporarily- then make sure "Enable debugging mode" is turned on, and run a new scan? paste any error message you may get here to check.
This message "Scan process ended after forking" -mostly- is there because either one of your plugins is blocking access to wp-admin folder, or some codes in .htaccess is doing the same thing, you may need to check if your web host left some codes there doing that.
Let me know how it goes,
Thanks.