Thank you guys.
My problem was that i needed AI opponents in top-down perspective with full 360° movement which were supposed to patrol several positions. I first tried to avoid tracking their current facing/direction by myself and instead wanted to use their euler.z property to calculate their facing from by using the code in my last post.
This should have worked, but apparently the euler.z property is currently bugged. Now i tried your solutions which are keeping track of the object’s facing whenever they rotate. And currently this works like a charm. 