Cursor flickers excessively when STYLEREF field is used in header with multiple pages

[Performance & Graphic Issue] Word cursor flickers excessively when STYLEREF field is used in header with multiple pages 

Edit: This issue wont appear at the first time. You can try to edit for a bit time or just scroll a little bit and you will see flickers excessively in a unpleasant speed that ruins your whole writting experience... 

Description

I have encountered a reproducible performance issue in Microsoft Word that causes the text cursor (insertion point) to flicker excessively and continuously when a STYLEREF field is present in the document header.

Steps to Reproduce

1. Open Microsoft Word and create a new blank document.
2. Apply the "Heading 1" style to a few paragraphs in the body (e.g., "Chapter 1", "Chapter 2", ...). 
3. Double-click the header area to enter the header editing mode. Insert a STYLEREF field that references "Heading 1": Insert > Quick Parts > Field > StyleRef > Heading 1.
4. Close the header and add enough content to the body so the document spans approximately 5–6 pages (e.g., by pressing Enter repeatedly or generating dummy text).
5. Observe the text cursor behavior while typing or simply moving the cursor in the body.

Actual Result

• The text cursor begins to flicker rapidly and continuously once the document reaches about 5–6 pages.
• The flickering stops immediately when the header/footer area is hidden.

I Think the issue is directly correlated with the presence of the STYLEREF field in the header.

Expected Result 

The cursor should remain stable and not flicker, regardless of the presence of the STYLEREF field or the document length.

Environment 

• Application: Microsoft Word for Microsoft 365 
• Version: 2607 (Current Channel) 
• OS: Windows 10 22H2 (Build 19045) 
• Additional Info: This issue occurs in a brand-new blank document with no third-party add-ins or custom templates. The problem is 100% reproducible. 

Severity

This significantly impacts usability, especially when editing longer documents such as theses, reports, or books where chapter titles are commonly displayed in headers. The constant cursor flickering is visually distracting and causes eye strain during extended editing sessions.

Note

 

• The above report was drafted and translated into English with the assistance of Deepseek, but all the information provided is based on my own manual testing and observations. 
• The issue was discovered during my actual document editing workflow, and I have confirmed through repeated testing that it is directly related to the STYLEREF field.