Very little motion, eppur si muove: is it one?
Object closest to the right edge in the lower right corner moves only slightly and is blurred in frame 4.
Can someone more expert confirm it's an asteroid?
Sorry, that is just a regular star, it appears to move due to a slight misalignment between the frames (all other stars appear to move the same). Besides, the motion is not linear, i.e. from 2 to 3 is seems to be moving to the left but in 4 it jumps to the right (but again, all this motion is just an illusion due to tiny misalignment of the four images in the set)