Bug - Wrong Text

You add a cross reference to a heading.
You later go back and add some more text to that heading
When you update the cross reference it does not show the new/added text.

Steps to Reproduce

Create a new blank doucment
Insert the text "My heading 1"
Format this text with the built-in "Heading 1" style
Press Enter twice,
On the References tab, click on "Cross-reference".
Change the reference type to "Heading".
Press Insert to insert a cross reference.

Put your cursor at the end of the first line and type "more text".
Your heading should now be "My heading 1 more text".
Right mouse click on the cross reference and press Update Field.
You will see that the cross reference text has not updated to include the extra text.

On the Insert tab, click Bookmark.
Select the bookmark and press GoTo.
You can see that the bookmark does not include the extra text.

Solution - Move the Cursor Before

When you need to add text to an existing cross reference position the cursor at least one character from the end.
Type in you additional text and then delete the unwanted character.

Important

When you insert a cross-reference Word creates a hidden bookmark named "_Ref" followed by a unique reference number.
It is this bookmark name that the cross reference field refers to.
To fix an existing broken cross reference you will have to redefine the bookmark.