When multiple instances of RadEditor are placed inside hidden ASP Panel (visible='false') which is ajaxified with RadAjaxManager/RadAjaxPanel, and then the visibility of the ASP Panel is switched to true, the Statistics Module of the second, third.. Editors display 'undefined'. The issue is observed under Internet Explorer.

The workaround is to use:

-either ASP:UpdatePanel instead of the RadAjaxManager/RadAjaxPanel

-OR use the following JavaScript override:

            Telerik.Web.UI.Editor.Modules.RadEditorStatistics.prototype.doCount = function () {
            
                if (!this.get_visible()) return;

                var content = this.get_editor().get_text();

                var words = 0;
                var chars = 0;
                if (content) {
                    var punctRegX = /[!\.?;,:&_\-\–\{\}\[\]\(\)~#'"]/g;
                    content = content.replace(punctRegX, "");
                    var trimRegX = /(^\s+)|(\s+$)/g;
                    content = content.replace(trimRegX, "");
                    if (content) {
                        var splitRegX = /\s+/;
                        var array = content.split(splitRegX);

                        words = array.length;

                        var newLines = /(\r\n)+/g;
                        content = content.replace(newLines, "");
                        chars = content.length;
                    }
                }

                var elem = this.get_element();
                elem.innerHTML = "<span style='line-height:22px'>" + "Words:" + " " + words + "   " + "Characters:" + " " + chars + " </span>";
            }

In order to make the above function override working, it must be placed:

-Either below the RadScriptManager and load all the necessary resources through ScriptReferences of the RadScriptManager (disable the embedded resources of the RadEditors' instances too)

-OR create an additional instance of RadEditor in a hidden div, outside the AjaxPanel and place the function override below it.