Mid 2013 MacBook air screen with intermittent backlight. Any ideas?

My 2013 MBA ( MD760D) has some issues with the backlight. It starts for a few seconds and then dies. The computer is functional since I can use airplay and work on it using my TV but on the computer the screen blinks a few times and then is gone. ( I can actually see something if I use a flashlight on the screen).

I live overseas and decided to have it inspected by a local technician. He opened, no repairs at all, ( maybe moved a few things around like cables.) and it worked fine for a week. Now is blinking again and he suggested to change the motherboard.

The screen works (with backlight on for seconds only ), and it is perfect on an external screen. My first assumption is that I have something loose.

Any ideas on how to troubleshoot it?

your feedback is highly appreciated