Hello
I have the most recent ACF version installed (5.6.5) and in the backend of that plugin, the stylized JS chooser is broken – both on fields the plugin makes AND in the plugin itself (see attached screenshot for how I cant pick post types for relationships).
This seems to happen when I activate Events Calendar Pro .. when ECP is deactivated, the problem disappears.
I have reached out to the ACF people as well; however I wanted to make you aware since it seems that you are not doing the checking for the correct version of whatever “stylized chooser” you’re using OR maybe re-using a class or element name and hijacking it?
Please let me know your thoughts.