Posted by After installing Connections 5.5 and migrating the content, the wikis would no longer be editable. The richtext editor would not load.
The newly created lab environment without any customizations/data worked.
After digging around the system, I found that we had the some additional ckeditor widgets activated in the wikis.
Removing the file from /ConnectionsData/shared/customization/javascript/lconn/wikis/ckeditor.js and restarting common and wikis app resolved the issue.