A document contains a field in result mode different that the one specified in the export settings in the format providers (i.e. a field that need to be updated during the export), and this field is in a header/footer, and another header/footer contains a table with AutoFit to Window size. When this document is exported to docx or RTF, the table is exported with 0 width. The table is visualized splashed in RadRichTextBox, and MS Word behaves strangely and/or doesn't visualize the table at all.

The bug is regression in 2018 R1.

Workaround 1: Change the result mode of all fields in the headers/footers to match the one set in format provider export settings (Result by default) just prior the export.

Workaround 2: Set DocxFormatProvider.ExportSettings.FieldResultMode to null. For the default format provider used from the default Save command, use the following:
((DocxFormatProvider)DocumentFormatProvidersManager.GetProviderByExtension("docx")).ExportSettings = new DocxExportSettings() { FieldResultMode = null };

Fix available in LIB Version 2018.2.723.