I believe that there are some bugs in distance is calculated when one part of the equasion is in the air (jumping).

In a mission yesterday, I had rooted a melee mob and ran back (~20m) out of range to shoot at it. I managed to get an obstacle between myself and the target so I jumped to clear line of sight. To my surprise I was hit.

I stopped and watched the mob. It was still rooted and could not hit me if I did not jump. Yet each subsequent time I jumped I was hit by the mob.

This may also explain how I managed to get rooted from a altitude of over 40 meters a few days back. Jump-casting works in the game (tested), even though you get a message that casting isn't possible while falling.