To reproduce:
1. Create a canvas with an image
2. Create an empty child gameobject
3. Add a grid layout group to the empty child
4. Make the image a child of the grid layout group object
5. Add the image to the grid layout group - it's values are now driven by the grid layout
6. Remove the image from the grid layout - it's still driven by the grid
7. Make the image not a child of the grid - it's still driven by the grid

Note: removing the grid layout group component makes the image independent