I know it was a while ago that you posted. My daughter has recently (about 6 weeks ago) bought a S5 it has developed the gap across top and down left side. I notice you were going to contact Samsung, can you let me know how you got on. Thank you.
My gap is under the back button and when i press on it you can feel the screen lift up and down and its only 2 days old! thats really the only reason why i am worried when i press the back button you can see the light from under the screen