I’m using the latest 5.99 and when I export gerber files I get a format akin to a 2D drawing with borders and drawing footer.
When I import it into GerbView, I then get a drawing within a drawing…
I’m not using 5.99 yet, but I know in previous versions (like the stable 5.1.9 that I am using) there is a checkbox in the plotting dialog allowing you to enable or disable Plot border and title block. It is in a section called General Options. Look through your plot dialog for similar language. It is useful to have the border and title block for documentation reasons, but it often causes issues with automated gerber importers with many manufacturers.