Update: FIXED

After two days of attempts and many headaches i managed to get the tv running with (almost) no problems at all.
No taping solution worked for me, even though I tried different tape positions and lenght on both the main and the intercom ribbon cable.
After I simply swapped the two ends of the main ribbon cable (the one from mb to panel boards) the tv started. I then tried to put the cable back in the correct order and it worked as well.
My explanation is that, after some time, the heat coming from the chassis damages the bend in the middle of the ribbon...

Hello, I have a very similar problem with this tv: UE50TU8070U(XZT).
As you described, the tv continued to reboot about every ten seconds. I opened the back and disconnected the ribbon cable between the two panel boards and the tv started.
I could hear the starting melody but no picture on screen, which was backlit but black, like the panel remains undriven. The tv responds to IR inputs.
After some time i managed to understand that the cause of the rebooting was a short circuit between pin 1 and pin 46 of the mentioned ribbon cable caused by an internal short circuit between...