Jenssons Line Of Sight is a behavior with multiple attributes. Obstacles, Range, Collisions, and Cone of view.
You have to set Cone of View to less than 180 for it not to be able to see behind itself, and I would recommend 90.
Also, I'm using the most recent edition of Construct 2: 196.2; you're using stable release 195, which is the older copy. You won't have a lot of luck opening .capx files on this forum unless you're willing to update to the beta releases. https://www.scirra.com/construct2/releases