Uncaught TypeError: $template.get is not a function

Please see my answer here.

I fixed this bug by updating the html2element function to:

html2element: function(html) {
        var $template, attributes = {},
            template = html;
        $template = $(template(this.model.toJSON()).trim()), _.each($template.get(0).attributes, function(attr) {
            attributes[attr.name] = attr.value
        }), this.$el.attr(attributes).html($template.html()), this.setContent(), this.renderContent()
    },

in /wp-content/plugins/js_composer/assets/js/backend/composer-view.js

or in wp-content/plugins/js_composer/assets/js/dist/backend.min.js`

Hope this works for you!