poosible target ?.
Can an asteroid appear in some but not all images in a sequence.
It will usually be in all 4 images moving in a straight line, so unless it goes into or out of the set, or is hard to see because of a star, or extremely faint and hard to identify from background static, it should be in all 4.
In this image, there is an asteroid near the top moving up and to the right in all 4 images. Above it is a flat field defect, an artifact. Since artifacts usually move in a motion of up, down and right, then back to the left and slightly up, that is why it 'disappears' in frame 3, reappears in frame 3, then moves back up up and to the left in frame 4.
Note: if you put this in a look, it looks like it is moving down and to the right, disappear in one frame, but that is an illusion. You are viewing slides 4, 1, 2, 3 to see that motion. Straight line movement must be seen going 1, 2, 3 then 4.