Why do my parent and children move at different rates?

This is for 2D, though I don't think that is relevent here.

I have an object "Player" and a child object "Player Sprite". Each has scale set to (1,1,1). Player has a rigidbody2D. I have replicated this problem with all scripts on the objects turned off, and with a dummy object as a child.

Whenever Player is moved more than 2 units from origin, Player Sprite (the object itself, not just the image) still has a local position of (0,0,0), but is further in the given direction than Player. As the distance from origin increases, so does the discrepancy.

This is happening both with my physics-based movement in-game and simply using the editor to change Player's position. It's just weird. Does anybody have any ideas?

EDIT: The effect of in-game physics appears framerate dependent, or is at least intermittent. The porblem in the editor is constant.