Inserting media via "media browser" button in WYSIWYG does not return to editor

When inserting e.g. an image via the "media browser" button, everything works as expected, until the "submit" button is clicked. At that point, another popup should show allowing to choose the format of the image (e.g. large). Instead, the popup just disappears, but the lightbox shadow remains and the editor is not accessible anymore.

This happens regardless of editor and regardless of whether an image is uploaded, provided by URL or selected from the library.