Texture issue .. is it opacity map ?

[PhilippeV8]

I have attached 2 renders.

1 is a scaled down version of a 10K pixel wide render I did myself (7h render time).

The other is a 16K pixel wide render 3Dotp did with 24 samples.

The result from 3Dotp looks real crisp, but we get a weird triangle darker shape in the screens of the terrace covering.

The screen is a advanced material with a bumpmap to give it a fabric look and an opacity map with small perforations to make it semi-transparent.

I tried different things here on my computer to recreate the issue, but can't.  Even opening the files from the KSP file ..

If we can fix this, we're golden.