I had the same issue with a spontaneous crack. We didn't touch the tv and yet the technician said the crack was caused by external contact! So frustrated as we just bought the tv 2 months ago!
Description of the origin of the fault:
While watching tv the loud noise comes out of it and the line starts appearing on the screen. It turned out to be a internal crack on the panel.
No one touched the tv and we watched a spontaneous break.
After the guarantee claim we had a visit from a technician who just watched the television and wrote in the report just this:
"Although it has no external marks the screen is damaged"
Based on this report Samsung Portugal says:
"Although there is no point of impact on the frame, there may have been twisting or impact that caused the anomaly to report, however, we have no way of proving what caused the damage to the equipment, only ensuring that the features for which the equipment was manufactured would not lead to such anomaly. "
As I am sure that I did not reach or moved the TV I went to investigate and found that there are several identical cases.
There is also information from studies by samsung engineers mentioning the possibilities of the interior glass substrate being with micro faults which with heat may cause this anomaly :
The technical department in Portugal showed lack of knowledge and seriousness. And the only existing report, on which the verdict is based, is a ridiculously basic document .
Lack of care, rigor and seriousness has been clearly demonstrated by Samsung.