How can I avoid some 3d object faces being visible through walls?

Hi everyone,

sometimes some 3D-Object faces are visible through walls with no consistency what so ever.

The same object might be visible or not, with the same Z-Height and same walls.

in this example, the Vents on the roof are visible on the right of the screen, although they are behind the all in front of the player.

Replacing the object with a copy of itself sometimes fixes the issue.