Hi! Thanks for your answer. Well, the seams were generated automatically, however I see what you mean. The chamfer effect smoothens the edges by inserting small faces, and those faces are getting as lone islands on the UV map If I am not mistaken which have different normal vectors calculated even they are next to each other directly?
Coming out from your words it seems it is a manual edit now to solve the problem, probably by putting the seam edges somewhere else than the smoothed edges?
Thanks!