When adding a a Drag N' Drop activity it doesn't occupy the whole screen. It only occupies a half of the video. This only happens if the activity is set to show as a button not as a poster.
Issue reported in: https://h5p.org/comment/17776
Sample content: https://h5p.org/node/171182
Additional notes: I initially created the Drag N' Drop activity using the poster settings saving it and edited just to change the setting to "button".
Content created in H5P.org
There should be a way to have the activity occupy all available space in the video similar to how the "poster" setting works.