There are some JavaScript issues reported with WP4.6 and conflicts with other plugins, here https://support.advancedcustomfields.com/forums/topic/uncaught-typeerror-cannot-read-property-body-of-undefined/ and https://support.advancedcustomfields.com/forums/topic/tinymce-error/. The developer is aware of the issues and is working on a fix. Please see the other topics for some possible temporary fixes.
