On closer examination, and flipping between the first and last frame, I am convinced the large object is Phobos, and it moves to the upper right.

In the first frame, there are two bright objects that are smaller than the large bright one(Phobos). They are larger than the pixel size so I do not think they are incomplete data. One stays fixed between the first and last frame. Maybe this is Earth, or Demos. The other one disappears and I have no idea what that is.

Remember that Demos, orbiting farther than Phobos, would move slower across Mars’ sky.

I am still waiting for a color sunset(or sunrise) picture of Phobos, Demose, Earth and Venus all near each other.