Small white glitch lines flash up on Macbook screen after installing new LED screen.

Hi there,

Recently I decided I would manually fix up my old Macbook Pro in order to make some money by selling it on Ebay. The original issue was that its LED screen was broken after being crushed in the hold of an airplane. Only a small portion of the LED screen function normally, with around 75% of the screen covered in black or coloured lines or areas. I bought a brand new replacement LED screen from Ebay and ensured that it was the correct specifications for my Macbook Pro. I looked up a tutorial on how to switch the LED screen and I followed every step as carefully as I could, opening the machine up and taking the screen apart in order to fit the new one.

Once I fitted the new screen, the new screen was mostly working perfectly well, except that in a specific area of the right-hand side of the screen, some very small, narrow horizontal lines would sometimes flash up very quickly before vanishing again. The lines are very small and do not appear on an external when the Macbook is plugged into my monitor or TV, so I know the problem is related to the LED screen itself. Here is a video I took of the issue so you can see it in detail: LED Screen Issue - YouTube

At the moment I speculate that the problem could be due to one of these three things, but I am not sure:

1) I'm thinking the problem might be the replacement LED screen itself - do you think I received a faulty part?

2) Could it also be that I failed to reconnect the video cable to the back of the replacement LED when I installed it? As I said, I made sure I did everything as carefully as possible, so I doubt it was this.

3) Perhaps the video cable itself has a fault (the cable that connects the LED screen to the logic board). Perhaps I damaged it when I did the installation, if it is extremely sensitive? I have ordered a replacement video cable in case this is the issue, but I don't want to go through the bother of replacing it if that's not going to help.

If anyone could offer any suggestions on this, it would be very much appreciated. I will write the specs for this Macbook down below. Thank you very much.

Mid-2012 Macbook Pro (Non-Retina Screen)

MacOS High Sierra (Latest Update Installed)

15.4" Non-Retina LED Screen

750GB Hard Drive

8GB RAM

2.6GHz Quad-Core Intel i7 Processor (Turbo Boost up to 3.6Ghz)