This is an interesting bug I never encountered before, but since I tried your code, I also fail this level.
As workaround, try the following code:
x = 5
y = 5
enemy = self.findNearestEnemy()
x = x + 10
y = y + 10
It uses fixed coordinates and not relatives, but will do the trick for this level. The problem is that you walk around the target-zone, missing the goal-trigger.