Running headers are missing on 3 chapters, working fine on others.

I have used a previous book template for a new book. So I have updated the text variables to the new book title. I have gone through each A-Master in each chapter and inserted the new title. If there's an easy way to do this for all chapters at once, please let me know. Three of my twelve chapters will not display a running header even though it is in the A-Master. What has gone wrong and what should I do? Thank you.
