The coordinates of the subset are extracted as WKT from the rectangle of my interest took at the beginning from one reference image. Now the problem is that every subset seems to be cut in a different way:
I had exactely the same problem, reported in this topic:
but I used already the SNAP-6 version, using Tie-point geocoding instead of per-pixel geocoding. I found the only solution to be Un-abling the “Preserve resolution option” and resampling with Bilinear interpolation.