Simple reproducible is attached to illustrate the problem.

A workaround may be replacing RadButtons that invokes such postbacks with regular buttons and using a form decorator

Alternatively, you can simply disable the handler URL encryption

You can also put the following in the global.asax file to prevent the version from rendering on the page markup
        protected void Application_BeginRequest(object sender, EventArgs e)
        {
			System.Web.HttpContext.Current.Items["_!TelerikVersionStampRendered"] = true;
        }
or you can add the same line in a global Page_Load handler (e.g., in a base page class or in the master page your project uses)

If AllowPaging, AllowScroll and UseStaticHeaders are set to true, then there will be 2 empty <th> elements

workaround: 
    <ClientSettings>
...
        <ClientEvents OnGridCreated="OnGridCreated" />
    </ClientSettings>

<script>
    function OnGridCreated(sender, args) {
        var emptyth = $telerik.$(sender.get_element())
            .find("th").filter(function (ind, item) { return item.textContent == "" });
        // alert(emptyth.length)
        emptyth.append("<span style='display:none'>Hidden empty table header</span>")
    }
</script>

Images that reside in the grid will get resized (scaled down with about 3-5 %) which might cause issues, specially if exporting bar-codes, thus the bar-code scanners won't be able to read them.

Current workaround is to use the Telerik Documents Processing Library  and build the table manually where the images are inserted without changing the size.

Here is an example:

        protected void RadGrid1_InfrastructureExporting(object sender, GridInfrastructureExportingEventArgs e)
        {
            Telerik.Web.UI.ExportInfrastructure.Table table = e.ExportStructure.Tables[0];

            Workbook workbook = new Workbook();
            workbook.Worksheets.Add();

            Worksheet worksheet = workbook.ActiveWorksheet;


            foreach (var row in table.Rows)
            {
                if (row.Index > 1)
                {
                    worksheet.Rows[row.Index - 1].SetHeight(new RowHeight(55, true));
                }

                foreach (var cell in row.Cells)
                {
                    if (row.Index == 1 || cell.ColIndex != 2)
                    {
                        worksheet.Cells[cell.Index.Y - 1, cell.Index.X - 1].SetValue(cell.Value.ToString());
                    }
                    else
                    {
                        FloatingImage image = new FloatingImage(worksheet, new CellIndex(cell.Index.Y - 1, cell.Index.X - 1), 0, 0);
                        Stream stream = File.Open(Server.MapPath(cell.Value.ToString()), FileMode.Open);
                        using (stream)
                        {
                            image.ImageSource = new Telerik.Windows.Documents.Media.ImageSource(stream, "jpg");
                        }
                        worksheet.Shapes.Add(image);
                    }
                }
            }

            byte[] data;

            using (MemoryStream ms = new MemoryStream())
            {
                XlsxFormatProvider xlsProvider = new XlsxFormatProvider();
                xlsProvider.Export(workbook, ms);
                data = ms.ToArray();
            }

            Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
            Response.Headers.Remove("Content-Disposition");
            Response.AppendHeader("Content-Disposition", "attachment; filename=" + RadGridLista.ExportSettings.FileName + ".xlsx");
            Response.BinaryWrite(data);
            Response.End();
        }

Workaround 1) Use .resx files as the attached ones 

Workaround 2) Set properties to ViewState
        RadMonthYearPicker1.MonthYearNavigationSettings.ViewState["_mCancelButtonCaption"] = "my cancel";
        RadMonthYearPicker1.MonthYearNavigationSettings.ViewState["_mTodayButtonCaption"] = "my today";
        RadMonthYearPicker1.MonthYearNavigationSettings.ViewState["_mOkButtonCaption"] = "my ok";

The appearance problem can be seen on http://demos.telerik.com/aspnet-ajax/pivotgrid/examples/firstlook/defaultcs.aspx.

Click on the filter icon for Product name, you will find that the save and cancel buttons are off-screen. And if you hover over Label Filters or Value Filters the window is not wide enough to fit the popout menus that show:

There are missing keys in the resx files and the resource files are not applied correctly. More info here: 

• https://www.telerik.com/forums/localizing-radcolorpicker-using-resource-files

Workaround:

Placing the script below under the ScriptManager of the page:

kendo.ui.Chat.fn._resetToolbarButtons = function (j) {
    var k = this.wrapper.find(".k-toolbar-box");
    if (!k.is(":visible")) {
        k.show();
    }
    if (j.toolbar != false && "buttons" in j.toolbar) {
        this.options.toolbar.buttons = j.toolbar.buttons;
    }
}

Reproduction:

<telerik:RadChat runat="server" ID="RadChat1" Height="400px">
    <ClientEvents OnLoad="OnLoad"  />
</telerik:RadChat>
<script>
    function OnLoad(sender, args) {    
        sender.set_user({});
    }
</script>

Reproduction code:

protected void Page_Load(object sender, EventArgs e)
{
    RadToolBarDropDown dropDown = new RadToolBarDropDown("PageSize");
       
    dropDown.CssClass = "perPageDropDown";
    dropDown.EnableImageSprite = false;
    // dropDown.Text = GetGlobalResourceObject("Insight", "Per pagina")
    // dropDown.ToolTip = GetGlobalResourceObject("Insight", "Per pagina")
    FileExplorer1.ToolBar.Items.Add(dropDown);
}

<telerik:RadFileExplorer RenderMode="Lightweight" runat="server" ID="FileExplorer1" Width="595px" Height="350px"
    AllowPaging="true" PageSize="10">
    <Configuration EnableAsyncUpload="true" ViewPaths="~/"
        UploadPaths="~/" DeletePaths="~/"></Configuration>
</telerik:RadFileExplorer>

When the RenderMode property is set to Lightweight, File manager dialogs still load with Classic render mode, even when the <add key="Telerik.Web.UI.RenderMode" value="Lightweight" /> is set globally in the web.config:

<telerik:radeditor RenderMode="Lightweight" runat="server" id="mainRadEditor" EditModes="Design" >
    <Tools>
        <telerik:EditorToolGroup>
            <telerik:EditorTool Name="ImageManager"/>
            <telerik:EditorTool Name="DocumentManager"/>
        </telerik:EditorToolGroup>
    </Tools>
</telerik:radeditor>

This is causing rendering problems and some of the icons do not load.

Reproduction:

<telerik:RadMediaPlayer RenderMode="Lightweight" ID="RadMediaPlayer1" runat="server" AutoPlay="true"
Height="360px" Width="640px">
    <PlaylistSettings YouTubePlaylist="PL28149B23F489D223" Mode="Buttons" ButtonsTrigger="MouseDown" />
</telerik:RadMediaPlayer>

Scenario: RadButton within RadPageView part of RadMultiPageView integrated with RadTabStrip for switching PageViews.

When switching tabs, additional padding is applied to the text in RadButton. After a postback is made, padding is not applied anymore.

Using an ampersand character in RadBarcode's Text leads to a server-side error. Replacing the symbol with its corresponding HTML entity allows the control to render its text successfully, but the generated image corresponds to the passed entity character.

If RadBarcode1.Text="&amp;" the control generates this (read as "&amp;"):
https://www.screencast.com/t/NuOVjB8EY

while it should be this (read as "&"):
https://www.screencast.com/t/vOhWkUoW

Workaround:

When we generate the image by keeping ShowText = True, then it throws the exception.

When we generate the image by keeping ShowText = false, then it successfully generates the image.

Steps to reproduce:Run the following setup: