Video: https://www.screencast.com/t/rzmzuZ0UFa
Steps to reproduce:
1. Open in IE 11: https://demos.telerik.com/aspnet-ajax/editor/examples/overview/defaultcs.aspx
2. Insert a video through the Media Manager
3. Click over a tool having a drop-down menu (e.g. the Format tool)
Result: The heavy-weight object of the video is shown above the shown drop-down menu.
Use the solution provided in this KB to solve the issue: https://www.telerik.com/support/kb/aspnet-ajax/editor/details/inserting-a-video-tag-via-the-media-manager-instead-of-the-default-object-embed-ones.