This is what the master pages currently look like:
As you can maybe see, I set the margins to 25 mm on the outside and 15 mm on the inside. These used to be 30 mm and 20 mm respectively. After changing these margins on the master pages, I adjusted all the elements on the pages to fit these new margins (by widening the text boxes and extending the line at the top of the page).
The problem is, on the pages that follow these master pages, the main text boxes haven't changed. Only the text box at the top (which contains the italic text variable that you see in the picture) and the line under it change correctly on all the pages. Here is a picture of two random pages that follow the master:
Here you can see that the main text boxes haven't extended to the new margins, they won't change no matter what I do to them on the master pages. The top text box and line adjusted perfectly. It appears that there is a locked text box under the 'real', unlocked text boxes (containing text). This locked text box is the one that conforms to the master page but how can I make the unlocked text boxes conform while removing the locked ones?