Elements disappearing when you enter responsive mode and only appear when you click it

Question

As soon as my page is loaded, all the elements that fit on the screen are rendered, but as you scroll down the screen a little bit, the elements are not shown, they are only rendered when I click on them, and when this element is shown, another element at the top add (?)

1. Page soon when loaded shows all the elements that fit on the screen:

2. When scrolling down the page I notice that the elements are not being shown:

3. When clicking above, the element is rendered:

Has anyone ever been through it? I’ve tried some things like:

I checked if the Divs are closing properly where they should;
I checked if there are equal ids;
I checked if all ngmodel variables exist in ts.

I don’t know what to do.

Answer 1

For those who are interested, I use the bootstrap design material and when I changed their card to position: Ticky, the elements were rendered as expected. I don’t really understand why it worked