Image distortion issues like this tend to be the displays T-CON breaking down or spill damage (corrosion) around the connectors. Replacing the display is an easy job, but the cost of the part is quite high for a clean screen and only used. [https://www.thebookyard.com/product.php?cPath=39_1268_287&products_id=20279|Retina MacBook Pro 15" Complete Display, some Staingate (12/E13)] and here’s the guide [guide|9708]