editor.getData() returns invalid table in specific case

[kubaklatt]

📝 Provide detailed reproduction steps (if any)

1. Open for example https://ckeditor.com/docs/ckeditor5/latest/examples/builds-custom/full-featured-editor.html
2. Create a 4x3 table
3. Merge cells from the second row and second column to the third row of the third column
4. Set the first column as the header
5. Use editor.getData() to extract HTML
6. Use editor.setData() to implement the table into the editor

✔️ Expected result

editor.getData() returns a valid table without additional columns and rows

❌ Actual result

editor.getData() returns a table with additional columns and rows

Screen.Recording.2024-11-28.at.15.15.10.mov

📃 Other details

• Browser: Any
• OS: Any
• First affected CKEditor version: 37.0.0-alpha.1
• Installed CKEditor plugins: …

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[Witoso]

Could you check if this is a recent regression?

[kubaklatt]

@Witoso I managed to locate that the problem started occurring from 37.0.0-alpha.1

[Witoso]

Possibly a dup of #17404