My pwa redirects you to another url for auth. Doing so the bottom browser navbar appears. When redirecting back the navbar disappears because the pwa is in fullscreen.
The problem is that there is a white margin at the bottom. The body { height: 100%} is not taking up 100% of the screen.
This actually explains my problem exactly, however the answer is not really satisfying https://discussions.apple.com/thread/251535534