Mid 2011 iMac 12,2 black screens randomly

[mystxry]

I have an iMac 12,2 which has this annoying bug of randomly black screening. The fans run in the background and I can hear the OS sounds whenever I use my keyboard and mouse so only the display dies. Sometimes, It occurs whenever I lower my brightness from max and when I play some games on fullscreen but other times it happens randomly.

GPU: AMD Radeon HD 6900
Processor: Intel(R) Core(TM) i5-2400 CPU 3.10GHz
Memory: 8 GB RAM with 3 more empty slots.

Recently, I installed windows 10 on my iMac using OCLP and had just got around fixing the BSOD issue when this happened. This issue had persisted on my mac os as well.

One temporary and unreliable fix I cam across was to hold the power button and spam keys until the OS booted onto login. However this doesn't seem to work on windows.

If anyone could guide me to the right direction, I would really appreciate it because this is my only working computer rn.

Also, this issue doesn't seem to occur when I'm light browsing or doing menial tasks like downloading.

My default mac OS is high sierra 10.13

 

[Bigwaff]

If anyone could guide me to the right direction, I would really appreciate it because this is my only working computer rn.

One possible to web research…
The v-sync backlight cable or backlight board is going bad. When display go black, turn off lights in room so it’s dark, and shine powerful flashlight at display. If you see elements of desktop or application windows under flashlight beam, backlight the problem.

 

[mystxry]

One possible to web research…
The v-sync backlight cable or backlight board is going bad. When display go black, turn off lights in room so it’s dark, and shine powerful flashlight at display. If you see elements of desktop or application windows under flashlight beam, backlight the problem.

It isn't backlight as no icons popped up.

I'm positive its related to display drivers but my AMD doesn't seem to be faulty.

Also there's this weird blue line at the bottom which is persistent across every OS and interestingly goes out when my iMac blackscreens.

 

[mystxry]

Update: I resetted my SMC by unplugging my power cord and replugging after 15 seconds and just for that session, surprisingly, no black screen occurred. However, I booted back on without resetting my SMC and when in fullscreen, black screen occurred shortly.

Another thing I noted was this issue only occurred on my windows when I was in fullscreen for a short period of time (~15 minutes) and it seemed stable otherwise.