Consider three objects: a rubber ball, a spaceship, and an isolated brick wall floating serenely in the vacuum of space.
From the perspective of an observer on the spaceship, the ball is moving toward the wall, while the wall and spaceship are stationary. The ball collides with the wall and bounces off. After that happens, the ball is now moving away from the wall (and, by a negligible amount, the wall is moving away from the ball) while the spaceship is still stationary. This makes sense.
However, as I understand it, from the ball's perspective, it started out stationary, while the wall was moving towards it, and the spaceship was moving in the same direction as the wall. Then an event occurred. Afterward, the ball is again stationary (from its perspective), but the wall and spaceship are both moving in roughly the opposite direction as before.
But the thing I don't understand is, from the ball's perspective, how can an event that only involved the ball and the wall have affected the movement of the spaceship?