Frosted Glass banding artifact

We have been experimenting with getting a frosted film on glass to work in v2.3. For some reason once we start rendering at higher resolutions we are getting a banding effect that’s horizontal to the image. The higher the resolution the tighter the bands.

Both images have the same settings, just different resolution. Left is 1440x810 and Right is 3840x2160.

Using a 4k black and white noise map in the normal slot. Tried a 2k BW map, a 2k normal map, and a 2k blurry BW map.

Not sure what’s going on as we don’t see the issue on screen only when rendered out.

Any help would be much appreciated!

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Is this something that is due to the texture map or is this some kind of screen space artifact?