When opening a new modal window, I see two scrollbars. One for the iframe (good), and another one for the modal dialog container area (bad). The one for the dialog container is only there to scroll a few pixels. It's confusing to see two scrollbars and can result in some weird behaviors with scrolling.
Use Firefox or Chrome and open a modal dialog. Observe the two scrollbars. If it helps, I was using Drupal 9.5.8 with a front-end theme that's loosely based on bootstrap. Maybe it's related to that theme. I don't know.
Add some CSS to remove the extra scroll.
Active
1.3
Code
+1. Adding a static patch from the MR. Thanks!