Bug: overlays incorrectly render on top of map geometry at grazing angles

[Wheattttt]

Describe the bug

Screenshot from the attached testing map:

Here you can see that overlays at grazing angles (almost perpendicular to the camera) will stick out and display over top of any surrounding geometry. This can extend surprisingly far, going through almost any geometry depending on the circumstances.

(There's a decal at the far end of this tunnel that you can't even see, but it still renders through the wall if the angle is sharp enough.)

This is mostly unnoticeable on a textured map with normal decals, but becomes extremely noticeable when using any kind of brightly colored and/or unlit decals, which end up flashing awful brightly colored lines across the screen. Example from a specific map of mine:

To Reproduce

1. Open the map
2. Try to get a grazing angle on the blood decals in the holes
3. Observe

Issue Map

decalclippingtestvmfbsp.zip

Expected Behavior

Overlays should be correctly occluded/hidden by walls that are in front of them.

Operating System

Win11