Not an important bug. Just something to "smooth"
First a screen :
It's not easy to see, but there're 3 "columns" in the sky, just here :
And if you take a close look, you can see "squares" of black smoke at the base.
On the column to the right, you can also discern the pattern used above gases layers, with the small "bubbles".
It happens during meteor shower, after an impact on top of this building, because the bunker floor (panels and doors) are at the limit of the zone in which we can build something. The regolith masses are in the forbidden zone.
The black smoke squares are normal, because the smoke of meteors is displayed 2 squares above the limit. But the small columns should not be visible.
Build a bunker floor at the limite of the playable zone, and wait for a meteor shower.