From a cursory look at your AFCAD with ADE, I think the issue is that you have two taxiway links starting from the same parking, and they both can connect to the end node you specified and, since GSX likely took the one passing through the not closest to the parking, it might not have enough space to turn the whole airplane.
You must consider the pushback is not affected just by the airplane length, but by the overall length of the system composed by the airplane, the towbar and the pushback vehicle, so it needs enough space to fit a curve and, when it can't, it will do strange rotations to solve something that cannot mathematically solved otherwise.
Try using a target node that ensure it will use the other path.
