Brick Pattern Artifact in Volumetric Clouds

A licensee has reported seeing a repeating brick-like pattern in volumetric clouds when they overlap with very distant geometry (or at the transition between nearby and distant geometry). The artifact consists of 4-pixel-wide horizontal blocks with alternating row offsets.

From testing, this appears to occur only when using the bilateral upsampling path (r.VolumetricRenderTarget.UpsamplingMode=4). Other upsampling modes do not produce the artifact.

Steps to Reproduce

1. Open the attached repro project
2. Set "r.VolumetricRenderTarget.Mode=4".
3. Move the camera to the upper edge of the cloud layer and look toward the horizon.
4. Observe the clouds where they overlap very distant geometry (or at the transition between nearby and very distant geometry).
5. Reducing the screen percentage makes the artifact easier to see.
6. Using cloud materials with stronger contrast and shadowing also makes the artifact more apparent.