I just spent close to 48 hour trying to figure out what was causing this issue on my Joomla 3.6.4 site, and FINALLY figured it out, so I want to share what worked for me here, in case any other poor soul finds themselves in a similar circle of hell: The editor button plugin for wbAMP is what is loading the chosen.js script on pages where it is not needed: that is, any page with an editing field. Turned it off and eureeka: Community Builder back-end buttons work again.