Julmust: It works as intended. Your version is not bugged.
Sprite7 is a "end of cliff" and Sprite5 is a "ground tile".
Sprite5 contains Sprite7.
In the layout you have two Sprite7 for four Sprite5.
So when you launch your project, due to the nature of containers, the missing Sprite7 are automatically spawn in the layout.
Hopefully this modified capx will help you visualize the action of containers.
It is your project with simple events to hopefully make sense of what's happening.
When you put your mouse cursor over a Sprite7 the opacity of the associated Sprite5 is modified.