Prefabs that are dragged from Assets folder to be placed in the Scene, are offset from the mouse cursor, depending on how far the cursor is from the center of the screen.

Steps to reproduce:
1) Create a new project.
2) Create a cube.
3) Drag the cube to the Assets folder to create a prefab.
4) Drag the cube to Scene view.

Notice how the cube is offset from the mouse cursor. Moving the mouse closer to the center of the screen brings the cube closer to the mouse.

Reproduced on:
5.6.0a1, 5.5.0b5, 5.4.1f1