Thats not the problem, the person is facing the right way, but their speed is still in the same direction. I plan to rework it a little bit so that you have to be standing still anyways, but it's a strange bug!
Not sure if that will work but try to use RotateVectorAroundAxis on the player velocity and for angle use the number you get when you compare the two Z rotations of the portals. If you are also rotating some portals in X/Y you would also have to do the same for them.
