Help! I had this glitch in my previous copy of the game so i got the GOG version. I cant jump to the upper left!
Any fix?

The problem is not with your game, but your keyboard. Many keyboards have a limit to how many keys can be pressed at once, and which keys they can be pressed alongside. In this case, your keyboard does not allow the Up, Left and A keys to be pressed at the same time, causing this issue.