Reduction - Operation Sandstorm: Some weird shadow near the top-left dish

[WhenTanksFly]

South-east from the north-west objective is... this thingy. On a closer inspection, it's not a tear in reality, but a shadow that gets gradually less transparent from right to left: I haven't noticed any near objects that would be expected to produce such a shadow. Besides, I first thought there's no floor and that I'd fall off the map if I step on it (but it's actually perfectly walkable).