Undo from several days ago??
The question is regarding all walls loosing their line detail in 2D, not the invisible wall (3D).
See how the window protrudes the wall - this use to have lines marking the external edge of the external wall and show the gyprock/plaster etc. This would of been done days ago, however, I have only just realized.
Feels like a bug. Guess I've lost days of work again.