It is possible that the extra weight of the space gray paint, or the way that it dries when painted, places undue stress on the phone which causes the auto-bending.
The second possibility is that there is something they are not disclosing when they mention "space" in the color description. Is it possible that they harvested some space substance either from an asteroid that crashed or something that they got from some other non-conventional means? Maybe that "space" material creates a temporal and structural shift in the aluminum substrate when it is exposed to the rubbing of a person's jeans.