Problem with Vimeo embed responsiveness

I'm having a problem on the Vimeo video embeds on my coursepress website.
Whenever there is a Vimeo video embedded on Course or Unit, it will not properly set the player and leave some black lines above and below the video. It seems it's not properly fitting the video.
Check image attached.
The YouTube videos are fitting properly, problems are only the Vimeo ones. How can you help me fix this issue?
Thanks a lot.