imac 27 led failure - left screen dark

Hi,

The LED backlights on the left part of my iMac 27 (Model A1312) are almost dark or completely dark. I see the LCD image but the backlight comes and goes. I have been searching on the web what could cause this issue and found that I'm not the first person that has had this problem. There's even a class action lawsuit against apple (Apple sued over alleged iMac screen dimming issues - CNET).

This problem came a month after having the GPU replaced (at no cost in an Apple Authorized Service Provider in Argentina (Maxim LLC). The AMD 6970 GPU failed completely and, luckily, the issue was covered by an Apple replacement program (HT203787).

My question is if this dark half screen issue could be the result of the GPU replacement or it is another problem that this particular model has. Please advise on a possible solution. Below a picture of the screen issue: