From the Developer Note on the issue:
Here the content needs to be updated to convert ViewportUV to BufferUV as FHLSLMaterialTranslator::SceneTextureLookup() does.
Like @SumFX did, Epic could at least say HOW to update the content. Or the name of the file containing the FHLSLMaterialTranslator::SceneTextureLookup() source. Because it’s not easy to dig into the shader source files to find some specific method.