Editing correction results in unwanted text displaying

We had a page from a client today that came in with the wrong year in the folio.  We thought: no problem.  We'll just edit the year, change the 5 to a 6 and all will be good. 

However, after changing the single number, we found that a bunch of unwanted text all of a sudden showed up in the middle of their page. Here are a before and after screen captures:

BEFORE

AFTER

You can see the text in the middle of the page.  There are three items.  We were provided with other the PDF files and we do not have access to the original InDesign files.

The folio where we changed the number, I presume was on the master page as there were other pages in this section of their paper that had the same incorrect date. However, when we changed the date on those pages, it did not show the same problem.

Any thoughts?

thanks,

Andy