Issue 1 - Incorrect layout until Game View is resized :

- import the project attached in a comment further down called case_599998-UpdatedParenting
- choose 16:9 in the Game View
- open the "AttachScene"
- drag the prefab "BookParentPanelSolo" onto the "Canvas" GameObject
- notice that the book layout is displayed weirdly and partly not rendered (many RectTransforms have negative size)
- resize the Game View and notice that the book layout is displayed correctly

Issue 2 - Some RectTransforms instantiated at runtime have wrong positions :

- import the project attached in a comment further down called case_599998-UpdatedParenting
- choose 16:9 in the Game View
- open the "AttachScene"
- drag the prefab "BookParentPanelSolo" onto the "Canvas" GameObject
- press play, which instantiates the prefab at runtime (called "BookParentPanelSolo(Clone)")
- resize the Game View to ensure both versions have been refreshed
- compare the TabButtonAnimal GameObject under the "BookParentPanelSolo" and "BookParentPanelSolo(Clone)" objects and notice that the clone one has a different position.