Word Document Using Columns Not Modified, But Suddenly Displays Differently

I am using MS Word on my Windows 11 desktop.  I have been using a Word document that I created a couple of years ago.  The document uses Columns.

The last time I modified it was a year ago.  I tend to print it out every two days.

Suddenly, the document displays differently and prints those differences.  It now displays vertical lines below four of the five squares.

I moved the document to my Windows 11 laptop.  Same problem there.

I sent the Word document to my son who opened it on his Mac computer.  On his computer, it displays exactly as it should -- No erroneous vertical lines.

Again, I have not modified the document.  I thought maybe a Windows update may have caused the problem, but I don't see any Windows update in about one month.

I am displaying two images below, a "before" and "after" image.  The "before" (i.e., correct) image shows five squares and the alphabet displaying vertically.  The "after" image shows vertical lines below the first four squares.

Can anyone suggest a fix for this?  Repeating myself again -- I have not modified this file in a year.

Thank you.

Len Jacobson

First Image -- Correct display of the five squares and the alphabet displayed vertically

Second Image -- Incorrect display.  Vertical lines appearing below the first four squares.