Hi, It should go away when not overclocked. Some cards also require you to ramp up the power a bit to get rid of the black boxes and artifacts. Overall, there is risk though and depending on the manufacturer you might lose warranty if you increase voltage, and power to the card. But that might be the only way to get rid of artifacts, other than lowering to normal speeds. If the black boxes remain at stock speed you should RMA the card once you made sure it is not a software issue. I am quite sure it is not software though, as I have seen this before on OC cards in BF4.
Specifically it happens on Hainan Resort as you look towards the mountains in the distance, they tend to go black on a card that cant handle the overclock that otherwise...