How to reproduce:
1. Download attached project files
2. Create Canvas in Hierarchy Window
3. Drag "circle2" Sprite into Canvas from Asset folder
4. Change Game Window size

Expected result: After changing the size of Game Window, Sprite shouldn't change position.
Actual result: After changing the size of Game Window, Sprite changes possition to a specific point in the world.

Reproduced with:5.5.4p3, 5.6.3p2, 2017.1.0p5, 2017.2.0b9, 2017.3.0a5

Note: this occurs because dragging a sprite under a canvas creates a sprite renderer instead of an image, so it has a transform. Changing the canvas size modifies it's world position which moves the sprite renderer out of view.