Stripes Artifact Appearing When Using Multiple Mirrors in Local Mode

[Olliebrown]

I'm observing an odd artifact when I have a scene with multiple mirrors. I switched the various mirror components into local mode and set them to pass their texture to a specific renderer in the scene. In general, each one looks right but every so often some black stripes slowly crawl across the mirror at a very specific and repeatable distance.

I have a video example here: https://youtu.be/qCZzTZngyvA

Expected Behavior: Multiple mirrors in a scene should be possible if you set them to local mode and assign the proper renderer. They will not reflect each other recursively but the first bounce reflection should look right.

Observed Behavior: While it works in general, every so often some very noticeable artifacts appear of black lines crawling across the mirror.

Speculation: I'm wondering if this is a mipmap or LOD artifact since it comes in at a very predictable and repeatable distance to the mirror.