A licensee reported that if the r.SeparateTranslucencyScreenPercentage is not 100, then the custom stencil would not be correct in the separate translucency pass. Because the resolution of the custom stencil is not equal to the separate translucency RT.
[Image Removed]
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-138179 in the post.