First off, sorry you’ve had such a horrible experience with your GT-R. Although it is possible for your trans to be a lemon (certainly an anomaly), it’s more likely previous owner abused it and then passed these issues onto you. Did you buy it directly from the previous owner or from a car dealer? In any case, I understand your desire to move on, but you’ll probably take a hit on value or be passing this off to someone else in the same manner you got it (not a good move). Sending it to Shep trans in the US for examination and repair would be the best thing to do - spend the money to have it done right and be able to finally enjoy the car. Just my opinion.