Steps to reproduce:

1. Install Confluence (in this example Confluence 6.5.x)
2. Navigate to Administrations > Manage Add-ons > select System > then search for  "Confluence Collaborative Editor Plugin" > disable the add-on
3. (Expected)Navigate to Collaborative Editing > Page Not Found will be thrown 
4. Navigate back to Administrations > Manage Add-ons > select System > then search for  "Confluence Collaborative Editor Plugin" > re-enable the add-on
5. Navigate the Administrations > Collaborative Editing

Expected Behaviour

Collaborative Editing page appear without any problem

Actual Behaviour

The page failed to load indefinitely and message "Something went wrong" is thrown

Workaround

1. Run the following SQL query:

   select BANDANAVALUE from BANDANA where BANDANAKEY = 'plugin.manager.state.Map';
   

2. verify if the following line can be found:

    <map>
     <entry>
       <string>com.atlassian.confluence.plugins.synchrony-interop</string>
       <boolean>false</boolean>
     </entry>
   </map>
   

3. If the above entry can be found, proceed with manually resetting the plugin to default state
   1. ensure the plugin cache is also clear as per advice in the KB
   2. ensure to re-run the SQL query above to verify if the entry still can be found
4. Verify if the Collaborative Editing page is still appear with error