kd-55x9000e backlight blinking problem

hi everybody. i have an issue with my kd-55x9000e tv. it suddenly started to blinking. it seems like the backlight is blinking. you can see the problem in link below.

https://www.youtube.com/watch?v=dVyIUZxm...

i couldnt fix the problem but when i send the tv to another city to a friend he said if he connect his laptop via hdmi cable to hdmi 2 slot and go to settings of the tv and load a picture the backlight blinking stops but he has to do it every time when turning on the tv and the blinking does not stop with other devices. the tv has picture and light and the quality of the picture is the same as when i bought it but this blinking is really annoying. can you please give me a hint what is the problem? i have turned the tv light sensor off.