The issue occurs when a user opens the Rich Text Editor (RTE) in the Content Editor from a zoomed-in browser. The RTE modal window might pop up with the dialog buttons out of the window frame. The scroll bars do not appear, and a user is not able to scroll down and use the dialog buttons. This happens because Sitecore XP does not dynamically pick the modal window size according to the browser's settings.
As a workaround for the issue, you can manually add scrollbars to the modal window by doing the following: