I have no idea if this will help or not.
Check that you do not have duplicate walls in the same location - could even be in hidden layers.
They maybe trimming each other away allowing you to see through them?
Does switching to the Vectorial engine make a difference?
If that looks OK it may be an OpenGL issue.
Are your video drivers up to date?
Barry.
One of the forum moderators.
Versions 6.5 to 27
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11