GTX 980 ti Issues (Freezing, White Lines Across Screen)

Hello,

This is my first post here so please be lenient if some of the things I say are obvious or strange

THE SPECS:

To begin with, these were my specs before attempting to change anything:

CPU: AMD FX 6300 (initially overclocked to 4.1GHz, then down to stock 3.5GHz)
Motherboard: MSI 970A SLI Krait Edition
GPU: GTX 960 4GB (overclocked by 150MHz)
RAM: 2 x 4 GB DDR3 Corsair 1333MHz
PSU: Corsair VS650 (650W)
Storage: Sandisk 120GB SSD (x 2, then reduced to 1 when reinstalling Windows)
OS: Windows 10 Home 64bit

I connect through HDMI to a Sony Smart TV at 1080p native resolution.

THE ISSUE:

I bought a used GTX 980 ti that was supposed to be in good condition (the store says they give 1 year warranty on those) but I had issues pretty much from the moment I installed the card.

To begin with, the display was locked at 800x600 resolution, whether it was in the BIOS or having booted Windows.

Then, I started getting issues with white lines across the screen, initially during Windows' boot logo but then even during BIOS. Another issue appeared when attempting to Safe Boot, uninstall the drivers (using DDU) and then reinstall the latest ones from Nvidia's website - as the installer is progressing, the screen will freeze and there will be nothing but a black background and white lines - that's it - I have to force shutdown or reset to make anything happen.

I thought it may have been the PSU's fault so I replaced it with a Corsair CS850M (850W) but nothing changed.

I have also attempted to reset the CMOS (which, on my MB is done by removing the battery and then reinstalling it since there is no button or jumper) and nothing changed.

I have reset Windows, then completely formatted my drive and reinstalled it, and yet nothing has happened in terms of a solution or improvement.


Here are some pictures of those issues:







The only time everything works in a fairly stable manner is when I boot into safe mode, but the resolution is still locked at 800x600.

CONCLUSION / QUESTION:

I have replaced the GTX 980 ti with the original GTX 960 and things are working fine, but I would very much like to use the former, obviously.

Could you please tell me if there is something I have not tried or whether I should try certain steps in a specific order? I have spent about an entire day's worth of time and this and I'm losing my mind. I would like to know if there is anything I can do before I conclude that I have a faulty product on my hands and have to either try to get my money back or get a replacement.

Thank you very much in advance!