Why doesn't position: fixed work on the page?

Question

css

I noticed on the "buy in one click" ( page ). A window appears ('clicklite clicklite_active'), which in the styles is fixed relative to the window, but in fact works as if it is absolute relative to the entire document. For example, give this element bottom:0 and turn off top, and you'll see that the element doesn't stick to the bottom of the window, but goes down somewhere.
Moreover, if any other element on the site is given position:fixed, bottom: 0, the element is anchored not to the bottom of the window, but to the bottom of the page.
Can you please tell me what could be causing this behavior?

Answer 1

will-change: transform; or transform
must be removed from main and other parents
Or pull out the modal from these blocks
Transform creates its own coordination system inside the block area, with its own rules and positioning, so it is fixed and flies down the drain.