Backlight and charging problem

Hello,

I have a MacBook Air with water damage (probably - the only element with red marker was a flex cable between boards).

The system works but only with a charger (no light on it) and is noisy. The LCD backlight works only if the flex cable is not connected (thats probably cause for the fan spinning high due to missing values from sensors located on audio board).

Once I connect flex cable the backlight is gone and after a few sec system will shut down.

I have found that backlight is gone when lower part of flex cable is pinned (the one closer to the hinge).

I have disassembled the whole laptop and found no place of gunk or corrosion. I have changed flex and audio board but without success.

Any advice what should I check? I have multi-meter and soldering tools.

I have done some photos:

Side A

Side B

and the connector itself: