When a DropDownList SDT form is saved in a XAML document and then imported with the XamlFormatProvider, an extra ListItem entry is added in the items collection of the DropDownList. The extra entry is the default "Choose an item".

To work this around, iterate all ComboBoxProperties and manually remove duplicates of the "Choose an item" entry.

var dropDownLists = radRichTextBox.Document.EnumerateChildrenOfType<SdtRangeStart>()
     .Where(x => x.SdtProperties is ComboBoxProperties)
     .Select(x => x.SdtProperties).OfType<ComboBoxProperties>();
 var defaultItemString = LocalizationManager.GetString("Documents_ContentControlsGenerator_ListItem");
 foreach (var item in dropDownLists)
 {
     if (item.Items.Count > 0 && item.Items.Any(x => x.Value != defaultItemString) && item.Items.Any(x => x.Value == defaultItemString))
     {
         var occurrence = item.Items.FirstOrDefault(x => x.Value == defaultItemString);
         while (occurrence != null)
         {
             item.Items.Remove(occurrence);
             occurrence = item.Items.FirstOrDefault(x => x.Value == defaultItemString);
         }
     }
 }

If the document contains a simple field without run inside, the import process fails. 

      <w:fldSimple w:instr="page" w:dirty="true"/>

The same document with a run inside the field does not cause an error

      <w:fldSimple w:instr="page" w:dirty="true">
        <w:r>
          <w:t>1</w:t>
        </w:r>
      </w:fldSimple>

RadSyntaxEditor, while inside of a virtualized RadGridView, stealings focus immediately upon loading. It appears to do this automatically and there is no configuration to disabling. Meaning when scrolling in a RadGridView with virtualized rows, when a row with the RadSyntaxEditor materializes it will automatically steal focus from other elements.

This can be worked around using custom behavior that discards the first preview keyboard focus event that it receives.

private void onPreviewGotKeyboardFocus(object s, KeyboardFocusChangedEventArgs e)
{
    if (!this.SuppressAutoFocus || _wasFocusSuppressed)
    {
        return;
    }

    _wasFocusSuppressed = true;
    e.Handled = true;
}

The offending line of code is this in RadSyntaxEditor.InitActiveEditorPresenter:

if (flag)
{
    base.Dispatcher.BeginInvoke((Action)delegate
    {
        Focus();
    });
}

Request: Add a dependency property to allow opting-out of this default behavior. The above workaround works, but is a bit hacky for something that should probably be built-in.

When using RadChat control and running the application, 2 binding errors appear in the Output Tab of Visual Studio.

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='Telerik.Windows.Controls.RadPromptInput', AncestorLevel='1''. BindingExpression:Path=Padding; DataItem=null; target element is 'RadGlyph' (Name=''); target property is 'Margin' (type 'Thickness')

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='Telerik.Windows.Controls.RadPromptInput', AncestorLevel='1''. BindingExpression:Path=Padding; DataItem=null; target element is 'RadGlyph' (Name=''); target property is 'Margin' (type 'Thickness')

Some of the lines that should be dashed are rendered as continuous lines.

There are missing characters when importing documents containing Standard fonts with a Differences array defined in the Encoding, which contains characters that do not fit in the first 255 glyph definitions in the font. Most of these characters are the ones with an accent such as "ccaron" (č).

The slow performance when creating thumbnail is only reproducible with specific documents.

Environment:

• Visual Studio 2026 Version 18.6.1 (May 2026 release)
• Visual Studio language: Japanese
• .NET 10 WPF project
• Telerik UI for WPF 2026.2.520
  

Problem:

Visual Studio freezes frequently while editing XAML when using Telerik UI for WPF 2026.2.520.
The issue does NOT occur with Telerik UI for WPF 2026.1.415.

Steps to reproduce:

1. Install the "Progress Telerik UI for WPF Extension"
2. Create a new WPF project using the Telerik extension/template (Empty)
3. Open the automatically generated MainWindow.xaml
4. Inside the existing <Grid> element, type:
   <Grid
5. At the moment XAML IntelliSense/code completion is triggered, Visual Studio freezes

Additional information:

• XAML Designer is disabled
• Deleting the .vs folder does not help
• No third-party Visual Studio extensions are installed
• The issue only occurs with Telerik UI for WPF 2026.2.520
• Downgrading to Telerik UI for WPF 2026.1.415 resolves the issue completely
  

Could you please confirm whether this is a known issue related to Visual Studio 2026 / .NET 10 compatibility?

This behavior is observed when the Pane is dragged and dropped near the Compass border (but not on it) several times.

The busy animation keeps running on the background when the busy indicator control gets unloaded (removed from the visual tree).

To work this around, set the IsBusy property of RadBusyIndicator to False in its Unloaded event handler.