I got a rectangular div element on a website with position: fixed and right: 20px and bottom: 20px.

On some websites, everything works perfectly fine. On other websites however, it takes roughly one second for the div to snap into the correct position (see video below).
This is weird, because a webapp running locally on my machine works fine, while the deployed version (on Vercel) has this jumping effect. It’s the same application, just on different environments.

I cannot test it as the local version works fine, so here’s a short demonstration.

I would appreciate any hints on where this issue could be!