Hello 
This is a long-standing issue that occurs in the topic when you try to type something into a modal input field. It always jumps to the top of the page, which results in an infinite load until it reaches post 1. It’s still an issue with the Glimmer Post Stream.
It makes very difficult to move posts to another topic because the modal also jumps while loading, other write related process and it also causes problems with the new discourse reaction feature, which opens the emoji picker. When it opens, it automatically focuses on the emoji search input, which produces the same behavior. It jumps to the top of the page and closes the emoji picker… So it happens when the modal input field focused.
This issue seems only happens on iOS.