Your header has three fields in it, at least one of which does not belong there.
00 deleteme 1.png

There is no reason for a TOC field to be in a header. I suspect that field is what is causing at least part of your problem, but it could be the Ref field.

Read the information on the StyleRef field and decide if that might be what you want to be using instead of the Ref field. I think you do. Then you would not have to unlink your headers and put in a different ref field.

If there is a reason you want a TOC field, tell us and someone will tell you what to use instead.

You can likely get rid of the \* MERGEFORMAT switch from each of these fields as well.

I'm amazed that your document worked at all with a TOC field in the header.
That is a Table of Contents field.

By the way, the Alt+F9 command controls the setting on your computer to display field codes. It does not change the content of the document at all. Remember to use it to toggle the display back when you are done looking.