Text box moving with page but covers footer, and not header.

HI d'

I think that with another look at the available object positioning rules you'll find that "move with page" is not an available choice.

"Stay on Page" will keep the object (in this case, a text box) in the position where it was set on the page, and "Move with text" will produce the result you are describing.

Move with text pushes the text box (or other object) down the page as text is added above that object. At the bottom of the page space allocated to text, the object will slide under the text boundary and out of sight…until it is pushed further down the document by added text which causes the text space on the upper page to be completely filled. At that point, the object is moved another line down, pushing it into the text space on the next page, and reappears in that location.

"Is this a bug

No.

or is there a setting I can change to stop this happening?"

Yes.

Set the object (text box) to Stay on Page, and let the body text flow around it.

Regards,

Barry