How to make slides appear at the top of each other inside a sticky section

Hello community,
I am trying to make some pictures appear on the top of each other with opacity, but the animation is not smooth at all. Also, the 3rd image that needs to appear is not the right one, and I don’t really know what’s wrong. Overall, the whole animation feels weird and laggy.
I used a cache wrapper to create the animation and set the z index to 0, while the sticky wrapper is 1.
I am attaching here the link to the page:

Here is my site Read-Only: LINK
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