If the main document part of a DOCX document is with name different than "document.xml", for example "document2.xml", the content of the document is not imported. 

Such documents are created by OpenXML SDK, if for example this tutorial is followed:
How to: Convert a word processing document from the DOCM to the DOCX file format - http://tpdogfood.telerik.com/msdn.microsoft.com/en-us/library/office/gg188063(v=office.15).aspx.

When a span element's opening and closing tags are on different lines in the HTML and there is no content in the span, it should be imported as a single space.

For example, the following HTML:

test,<span>
</span>test<span> 

should be imported as

test, test


Note: If there is content in the span that is split between the lines, it is correctly imported:
test,<span>a
</span>test<span> 

results in

test,a test

<samp> HTML element could be imported as span with specific formatting. Currently it's just ommited.

Currently, exporting to HTML serializes the containers by exporting them to XAML and adding them in a comment in the HTML. There are InlineUIContainerImporting and InlineUIContainerImported events, but the Handled property of the importing event arguments is read-only. This prevents users from creating their own serialization/deserialization logic.

Steps to reproduce:
1. Subscribe to events of the format provider:

            HtmlFormatProvider prov = DocumentFormatProvidersManager.GetProviderByExtension("html") as HtmlFormatProvider;
            prov.ExportSettings.InlineUIContainerExporting += ExportSettings_InlineUIContainerExporting;
            prov.ImportSettings.InlineUIContainerImporting += ImportSettings_InlineUIContainerImporting;
            prov.ImportSettings.InlineUIContainerImported += ImportSettings_InlineUIContainerImported;

2. Insert inline UI container in the document and export it to HTML. InlineUIContainerExporting event is raised and you can set the CommentContent property of the args to custom value.
3. Import the document back in the control

Expected: It should be possible to set the Handled property of the importing event args to true, and assign your desired value to the InlineUIContainer property.
Actual: InlineUIContainerImporting event is raised, but all properties of the event arguments have private setters.

The tab is inserted from the wrong side when the paragraph is with RTL direction.

When a RadDocument is created programmatically and its layout mode is set to Flow, the export to PDF doesn't respect section properties.

Adding a style with a specific name through the dialog, removing it and adding it again through the dialog causes an error. 

If style is applied to some document elements and this style is deleted through the Change Styles dialog, currently visible document elements (paragraph, spans) are not affected and retain the formatting as if the style is still applied.

Steps to reproduce:
- Add some text
- Select the text and create new style with distinguishable formatting, e.g. red forecolor. The style is applied to the selected text.
- Delete the style
Expected: the paragraph gets Normal style, and its forecolor becomes the default black one.
Actual: the Paragraph has still the custom paragraph styling

When RadRichTextBox for WPF is hosted in a WinForms application (through ElementHost), typing with Japanese IME duplicates the typed letters, which makes the control unusable with the default behavior.

Possible workaround: Create custom caret. There are some suggestions in this forum thread: https://www.telerik.com/forums/richtextbox-doesn't-support-japanese-ime-when-hosted-in-winforms

When spell checking dialog is used for spell checking, and the user proceeds to the next word (either by changing with a suggestion, ignoring, etc.), the view port is not scrolled to include the next currently spell checked word.

Fix available in R3 2018 Official Release.

Images nested in merge fields are imported as raw RTF text which leads to slow performance.

While typing in RadRichtextBox using Korean (Microsoft IME) keyboard "space" or "Enter" repeats the last typed character.

Workaround: Create a custom caret (example for custom caret) and override the EnableAsynchronousTextInsertion property so you can set it to false.

When underline style is already applied to a text, the style cannot be changed from the Font Properties dialog.

Workaround: Use the dropdown button in the ribbon.

Steps to reproduce:
- Select text.
- Open FontPropertiesDialog (or use ribbonButton for Undelinetext) and set underline style "Line".
- Submit the dialog.
- Right-click on the selected text again.
- Choose "Font..." from the context menu to open FontProperties dialog again.
- Change the underline style.
- Submit the dialog.
Expected: The selected underline style should be applied.
Actual: There is no applied underline style on the text.

Fix available in R3 2018 SP1 release.

When the rtf document contains a table as the one below and the empty declaration is used in the following structure, the document cannot be imported:

{\fonttbl
{\f0 Verdana;}
{\f1 Times New Roman;}
{\f2 ;}
{\f3 Segoe UI;}}

When the unit type is set to an inch:

Expected: to could be able to place the RulerThumb on every 1/16 of an inch.
Actual: be able to place the RulerThumb to every 1/8 of an inch.