Why do page and line numbers not show up properly

I type legal documents for circuit court and required to have 25 lines per
page and line numbers on every page. Some of my jobs are hundreds of pages.
Everything works fine until I get past page 150 and then in the bottom left
hand corner where it tells you what page number and line number you're on,
the page number doesn't change and the line numbers start going past 25 and
will go up to 999 and then neither the page or line numbers will change. How
can I fix and/or prevent this?