When adding videos through widgets such as the Formatted Text widget and Featured video widget, the video preview (thumbnail) and video playback are shown partially. There are no options available to auto-fit or resize the video thumbnail or playback either.
This issue was identified as a bug and resolved in Jive Cloud release 3006.9 with the issue key JVCLD-122518 (release notes on Worx). While the Cloud upgrades are automatically deployed, if you haven't yet been upgraded or have chosen to stay on an earlier version and now would like to upgrade, please get in touch with your Account Manager/Executive to arrange for the upgrade.
After the upgrade, the video thumbnails and playback should be displayed properly without being cut off.