Perhaps run the design checker tool, and see if that tells you anything.

Have you used the insert html code fragment tool to insert some code near
the navbar? Try moving the code fragment box off the page into the scratch
area and test to see if it is causing the shift. You may need to resize the
code fragment box to actual size.

If there are any other design elements touching, or near the navbar, try
moving them into the scratch area, or away from the navbar to see if they
are causing the navbar to shift. What is to the left of the navbar that
might be pushing the navbar to the center?

DavidF