I know this has been reported under previous versions, but I wanted to make sure you are aware that this is still happening under 1.72.496532:

The first screen snapshot below shows that I have 9 citizens, but only 6 of them are visible.  If you move your cursor to the blank space on the first row the hover popup will show 2 of the missing citizens and if you move your cursor to the blank space on the left of the second row the hover popup will show the third missing citizen.

I would give you a save file but, when I save the game, exit the game, restart the game, and load the save file, all of the citizens are visible as shown in the second screen snapshot below.

Good luck figuring this one out!