Hey! I just had the same problem with WP 4.2.2. I figured out that, the toViews function does not exist in that, so I checked for similar functions. In the wp-includes/js/plugins/wordpress/wpviews/plugin.js | plugin.min.js you must set the event.content = wp.mce.views.toViews(event.content); to event.content = wp.mce.views.setMarkers(event.content);.
