Hope someone comes up with an answer soon; but tell us about blanks/reflow in case it helps.
There are blank areas in the FM file.
Sometimes the entire page is rendered blank
I did try PgUP/PgDn
Use ctrl+L to refresh your screen. If the areas are still blank, then check to see if there are updated video drivers available for your hardware. If you have the latest, then is there a specific font that is not showing or is it any font?