@saeniv - Before you do anything drastic I would inspect the display connector area. often I find the pins are damaged in someway so one of the LED sets is not powered.
Post a few pics so we can see your connections Adding images to an existing question
I don’t blame you, opening the display assembly is not easy! So let’s look deeper into the logic board side of things.
While the display connector looks good we need to look on the other side of the logic board at the LED driver and its discreet components. Here’s a view of the logic board
And here’s a deeper view
Now lets look at the schematics for the driver
The first thing is to inspect the area so see if you see any signs of wetness and/or corrosion. Take a nice tight clear picture of the area and post it here if you are unsure so we can see things.
Basically I would locate the pin on the chip place my Ohm meter on that location and then find the display connector corresponding pin referencing this schematics snippet. Basically I’m looking for the lines resistance ~ 10.2 Ohms