UN50AU8000F: picture turns dirty green and the TV restarts

Problem:

soon after warranty expiration, the TV display started turning dirty green and restarting. It would work for a couple of minutes with no issues, then a screen-size blob appears and the TV reboots. After this, it just falls into the blob-reboot cycle without working properly even for a minute.

I've spent some time trying to understand what causing the problem, here are my findings:

• the backlight seems to work just fine;
• the power board works fine (or so I think);
• when I disconnect the ribbon cable from the main board, the problem does not reproduce itself (obviously, there's no picture, but I do hear the sound and the backlight never turns off);
• when I disconnect the right LED strip, there's no picture, but judging by the sound the TV does not restart;
• when I disconnect the left LED strip, there's no picture, but judging by the sound the TV does not restart;

By now I watched a ton of youtube videos (most of them are the "fix your TV with just tape" type), but was not able to identify the solution.

Any advices would be appreciated!