Steps to reproduce :

- create a new project
- create a Canvas and an Empty Game Object
- add the Horizontal Layout to the game object and make it a child of the canvas
- add a button, a text and an image as children of the Horizontal Layout and notice the are aligned
- create a Slider
- add it as a child to the Horizontal Layout and notice that it's not aligned with the rest of the elements
- create a Scrollbar
- add it as a child to the Horizontal Layout and notice that the Slider is not visible anymore

*Note :
Same issue with Vertical Layout.