Unknown quest area in desert

I am currently in part 2 (playing as 9S), and there is red area - like for quests, in the desert. But it does not relate to any of my active quests. It appeared also during the part 1 (playing as 2B). I wandered through that location many times, even with dynamic sensor active, and found nothing. What is it and why does it appear? Is it some part of weird quest? Or will