Sentinel-1 polarimetric decomposition problem


I am doing my Master’s internship and I’m working on polarimetric analysis of a Sentinel-1 SLC IW dual-pol VV/VH image.
I debursted the original image, generated the C2 matrix and the image is correct. But when I apply the H/A/alpha dual-pol decomposition, the result contains narrow horizontal stripes…

Where can this come from ?

I am using the latest version of SNAP (2.0.2).

Thanks for your help.