1: ready the portal skill so you are aiming it somewhere
2: try to aim it onto a surface higher tall enough to require jumping onto but not taller than your character (see attached picture for example of required height)
3: ta-da you crashed the game, it can be recreated anywhere you can find a place that meets the requirements in terms of height
so much as AIMING the portal onto that ledge infront of the character casues the game to hard crash, the same for any other ledges of that height, and I know you're meant to be up there, fro crying out loud there's literally a quest objective on the ledge