When trying to export a document containing InlineUIContainer inside a read-only range, the XamlWriter.Save() method that is used in XamlFormatProvider.Serialize() throws StackOverflow exception.

Sample code to reproduce the exception:
InlineUIContainer container = new InlineUIContainer();
Button btn = new Button();
btn.Content = "Sample Button";
btn.Width = 70;
btn.Height = 30;
container.UiElement = btn;

ReadOnlyRangeStart start = new ReadOnlyRangeStart();
ReadOnlyRangeEnd end = new ReadOnlyRangeEnd();
end.PairWithStart(start);
this.rtb.InsertInline(container);
this.rtb.Document.Selection.SelectAll();
this.rtb.InsertAnnotationRange(start, end);

XamlFormatProvider provider = new XamlFormatProvider();

string content = provider.Export(this.rtb.Document);
File.WriteAllText(@"c:\temp\asd.xaml", content);

When a table is dragged after a page break, and then Undo/Redo is performed for the drag operation NullReferenceException is thrown.

KeyNotFoundException is thrown when loading a document with a custom bibliographic style applied.

As a workaround, you can change the current bibliographic style to one of the predefined styles before the export of the document.

...
this.radRichTextBox.CommandExecuting += RadRichTextBox_CommandExecuting;
...

...
private void RadRichTextBox_CommandExecuting(object sender, CommandExecutingEventArgs e)
{
    if (e.Command is SaveCommand)
    {
        this.radRichTextBox.ChangeBibliographicStyle(new APAFifthEditionStyle());
    }
}

Korean language input does not work correctly on Windows 11 versions after 22H2 (OS Build 22621.1265).

This is related to an update to the Microsoft Input Method Editor (IME). The workaround is to enable the "Previous version of Microsoft IME" (check the attached screenshots for the steps).

When text is using fonts with defined ligatures (e.g. Calibri, Gabriola, etc.) and contains character groups with defined ligature for it, the text width is measured incorrectly (shorter that it should be). As caret and selection navigates on positions computed by this measuring system, they are not synchronized with what is shown in the UI (which correctly respects the ligatures), and there is slight offset from the real character positions and/or clipping of part of the letters at the end of the line.

Examples of such groups are (depending on the font) "tt", "ff", "ffi".

Importing a document with block-level content controls from XAML causes them to become corrupt. If you scroll to a position in which the said control is only partially visible a NullReferenceException is thrown.

A possible workaround would be to initially save the document as a DOCX (just exporting it to DOCX will not fix the issue as the information is already corrupt).

Another way to reproduce this issue:

1. Create a new document and insert a Rich Text Content Control.

2. Save the document as a XAML file.

3. Reopen the XAML file.

4. Move the caret inside the Content Control.

5. Try to insert a new line by hitting Enter - no new line is added as the content control is marked as Inline Level after the import in step 3.

Case 2: 

Create a document with TOC where the content control of the TOC contains some other inlines.