Automatic numbering in captions out of sequence

[Savager]

I am writing a document in which a lot of pictures need number labels. I have used captions in text boxes with the hope that they will automatically renumber should extra images be added/removed.

The problem is they don't quite renumber right on a single image. In the attached picture, the image on the left shows what happens when I update the fields - the text boxes renumber wrong. I want them to look like the image on the right with numbers increasing systematically.