Hi AntoineNC, welcome to the community!
I would be happy to take a look at your layout and see what is causing the issue. Could you provide a exported copy of the layout, either in a private message or in a reply to the message?
Please could you also confirm the CMS Version you are using?
If you are not able to provide an exported copy of your layout, I would first recommend checking the layer setting for the region containing the video and comparing that to the layer setting for the region that contains the web content that is appearing on top of the video. If the layer number for the video region is lower than the other region that appears on top, could you reduce the layer value for the problem region and republish the layout, to see if the issue persists?