When RenderMode is set to LightWeight and ToolbarMode is RibbonBar, a JavaScript error is thrown.

If a long paragraph is copied into the editor, <br> tags appear in thea content without being added at first place. 

For the time being you can resolve this by adding the following script below the editor declaration:

<telerik:RadEditor runat="server" ID="RadEditor1" StripFormattingOptions="AllExceptNewLines"></telerik:RadEditor>

<script type="text/javascript">
    var oldStripFormatting = Telerik.Web.UI.Editor.Utils.stripFormatting;

    Telerik.Web.UI.Editor.Utils.stripFormatting = function (textHtml, clearValue) {
        if (clearValue === "ALL_NO_BRAKES") {
            textHtml = textHtml.replace(/\n/g, "");
            textHtml = textHtml.replace(/<\/p>/g, "<br/>");
        }

        textHtml = oldStripFormatting.call(this, textHtml, clearValue);
        return textHtml;
    }
</script>

when trying to use the Visual Style Builder with IE 11, I get error

"System requirements not met

The Visual Style Builder requires a modern browser.

You can either upgrade Internet Explorer, or try Firefox for better experience on javascript-rich applications, such as this."

RadImageGallery fullscreen mode overrides viewport meta tag set on page.
If the user sets the following meta tag:

<meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1, maximum-scale=1.0, user-scalable=no, height=device-height" />

initially the page is not scalable. When the Gallery enters fullscreen mode, the page is zoomed out.
And when you exit fullscreen, the page stays zoomed out, the gallery proportions are changed and fonts are smaller.

The layout of these dialogs in SharePoint's Editor is broken to the point where the user would be unable to use them. 

Issue: Export to Excel Functionality developed using Telerik Grid doesnt work in IE 11 browser.

In one my applications the Export to excel Functionality is not working in IE 11. When the export to Excel Functionality is button is clicked , it gives a blank excel workbook without any data in IE 11 browser where as this works fine in IE 8 browser. I have attached the document with screenshots.

Code snippets:

  //Start- script to enable controls after export to excel
    if (typeof (_spBodyOnLoadFunctionNames) != 'undefined' && _spBodyOnLoadFunctionNames != null) {
        _spBodyOnLoadFunctionNames.push("supressSubmitWraper");
    }
    function supressSubmitWraper() {
        _spSuppressFormOnSubmitWrapper = true;
    }
    //End- script to enable controls after export to excel

    function click_handlerConsumptionReport() {
        theForm.__EVENTTARGET.value = '__Page';
        theForm.__EVENTARGUMENT.value = 'Export';
        theForm.submit();
        theForm.__EVENTARGUMENT.value = '';
    }

Putting an SVG element in the editor content will throw an exception under IE.

Workaround (Make sure to add the script element with the fix right after the RadEditor declaration):

<telerik:RadEditor runat="server" ID="RadEditor1">
    <Content>
        <svg height="100" width="100">
          <circle cx="50" cy="50" r="40" stroke="black" stroke-width="3" fill="red" />
        </svg>
    </Content>
</telerik:RadEditor>

<script type="text/javascript">
    var oldMarkListItems = Telerik.Web.UI.Editor.WordListConverter.prototype.markListItems;

    Telerik.Web.UI.Editor.WordListConverter.prototype.markListItems = function(htmlText)
    {
        if (!htmlText)
            return htmlText;

        return oldMarkListItems.call(this, htmlText);
    };
 </script>

MetroTouch "DragHandleDown.png" resource appears to be missing from 2015.1.225.40 version of Telerik.Web.UI.Skins.dll.

Got the following in my event logs:

Event message: An error occurred processing a web or script resource request. The requested resource 'pTelerik.Web.UI.Skins|Telerik.Web.UI.Skins.MetroTouch.Slider.DragHandleDown.png' does not exist or there was a problem loading it. 

Checked in the .dll for any reference to said resource. Found instances of "DragHandleDown.gif" for other skins (Black, Office2010Black, etc.) but nothing for MetroTouch.

Executing a cut command when Track Changes are enabled in RadEditor results in unexpected rearrangement of the content.

According to current implementation of paste functionality for IE, the editor gets the pasted content by executing the browser's paste command - 
editor.get_document().execCommand("Paste", null); 
This does not paste anything when browser's security setting "Allow Programmatic clipboard access" is disabled.