Outsystems popup in Reactive applications is appended directly in the body as the last element. This is unexpected since the documentation mentions that we should target the div with active-screen class (OnReady notes).
Here is the current HTML of an opened popup:

We can see that the popup is outside the div.active-screen element.
This idea is to fix this behavior and append the popup to the div.active-screen.
Regards
Leandro Oliveira