Having a similar issue, the button no longer displays on ACF WYSIWYG fields. Also, there are issues toggling between the visual and code editors when a Brightcove shortcode is present in a post:
Uncaught TypeError: Cannot read property 'setAttribute' of null
at n.initialize (tinymce.js?ver=4.8:44)
at n.b.mce.View (load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,jquery-ui-core,utils,jquery-ui-widget,jquery…:471)
at new n (load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,jquery-ui-core,utils,jquery-ui-widget,jquery…:401)
at Object.createInstance (load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,jquery-ui-core,utils,jquery-ui-widget,jquery…:471)
at load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,jquery-ui-core,utils,jquery-ui-widget,jquery…:471
at Function.m.each.m.forEach (load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,jquery-ui-core,utils,jquery-ui-widget,jquery…:59)
at load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,jquery-ui-core,utils,jquery-ui-widget,jquery…:471
at Function.m.each.m.forEach (load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,jquery-ui-core,utils,jquery-ui-widget,jquery…:59)
at Object.setMarkers (load-scripts.php?c=0&load[]=jquery-core,jquery-migrate,jquery-ui-core,utils,jquery-ui-widget,jquery…:471)
at o.<anonymous> (plugin.min.js?wp-mce-4603-20170530:1)