What was changed in 2011 MacBook Pros in the repair program?

Hi all, first post here.

I had my MacBook Pro early 2011 15” repaired through the repair program dished out in 2015, I believe.

It had suffered multiple GPU failures beforehand so when the repair program came out I was happy to send my MacBook Pro in for the repair.

It came back with an Intel HD Graphics 3000 512mb and worked fine.

So here is what happened next:

• 5 years later and I am getting similar issues. The laptop booted up in a green-tinted screen and then got stuck on a white-ish background after logging in.
• I take it to the repair shop and was told it ‘s a GPU failure, as expected.
• There was no direct repair available. The only option I had was to find a 2012 logicboard to fit into my 2011 unibody. I chose to hold off this idea for a while.
• I bring my MBP home and a day later I decide to boot it in recovery mode (cmd+r). It goes to a white screen the fans go crazy and I just leave it. It shuts down after about 10 minutes.
• I then reboot it normally, and to my surprise, there is no green tint, all the colours are perfect. I log in and bam! I’m in, no issues.
• However, I then start to notice green lines, one flashes horizontally then goes away, and another vertical green line pops up on the left and is permanent.
• Also, opening browser and anything video related has a green glaze as if wearing night-vision goggles.
• I notice the black colours are affected and go green.

So, this has all left me confused.

Is it a GPU issue? Or a screen connection issue? Perhaps both.

Remember this is a MBP 2011 unibody that has gone through the repair program.

So a lot of information online is about disabling the AMD Radeon graphics, but my MBP is running on the Intel HD Graphics as mentioned above.

Any help on this issue would be greatly appreciated.

Thanks