When using "Insert Moodle Media" to add a Youtube video (from the Youtube repository) to an HTML editor, the preview of the video is cut off and displays only as a very narrow vertical strip. Please see the attached screenshot.

Note: this seems to be a problem only in the Formal White, Boxie, and Brick themes. The following themes display the video preview correctly: Anomaly, Arialist, Binarius, FormFactor, Fusion, Leatherbound and Magazine.

Steps to replicate:

1. Ensure YouTube repository is enabled on site.
2. Ensure the site theme (or course theme) is one of the affected themes.
3. Access the text editor in any course assignment, label, etc.
4. Click "Insert Moodle Media".
5. Click "Find or upload a sound, video or applet..."
6. Click on YouTube repository and search for literally any YouTube video.
7. Select the desired video; click "Select this file".
8. Review the video in the "Insert Moodle Media" box.
9. For the affected themes, the video will be cut off and not display the entire video thumbnail.

Expected result: The full width of the video is viewable in the preview window.

Actual result: The video preview shows only a very narrow vertical strip.