UI is a layer - and its paralax is disabled (0%)
On the Human layer (100% parallax). The UI layer is analogous to your HUD layer.
As you can see from the video, what we see is a small rectangular screen, this is the resolution of the UI layer. Dalya, I shuffle the mouse and we see that the map is large.
In your example, when we specify half of the viewing screen does not work, since the screen is larger.
So as soon as the screen moves, the problem began. But AllanR offered a formula that fixed all this.
Try to solve it. It works fine. The object spawns right at the point of the sprite.
Your example works fine if the screen does not require scrolling, that is, does not go beyond the monitor zone.