Slick carousel and colobox video / image display

I have set up slick carousel field formatter in a content type and used a field to store images & videos (youtube links). I have set up the carousel to dispay images & videos and to open colorbox when the main image is clicked. This works fine for the images but when the colorbox opens a window to display the video content all I can see in the overlay is the arrows to move to the previous/next content and a close button and an empty square where the video should be playing. I can hear the audio playing but cannot see the video.

Link to image showing empty video colorbox.

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