Working on a house design, and on one of the floors, the walls aren't showing up properly. They should look like the wall in the first screen grab, but they look like the walls in the second screen grab. I am FAR from an Archicad expert, learning first Cadkey, then Autocad, then Archicad, so I am at a loss.
Difficult to say from your drawings as there are a lot of possible reasons, but starting with a couple of easy ones... Do the walls on the second floor project up into the third floor? If so, you should check the height of the walls and the "Show on stories" setting for the missing walls. Assuming the drawings have been placed from the View Map onto the Layout, you should check the view setting Layer Combination. If these are different between the floors, then the layer for the internal wall may be turned off on the third floor Layer Combination.
Apple iMac macOS Big Sur / AC24UKI (most recent builds)
The walls start on the first floor, go up to the second and third floors. They are set to show up on all relevant stories, layer settings has the walls turned on, cut plane is set properly, walls projected with overhead, entire element, model view options and graphic override are set properly