When overriding the catalog_product_view.xml, it seems that the changes in ProductVideo are no longer applied – so the line has to be added manually:
<container name="product.info.media" htmlTag="div" htmlClass="product media" after="product.info.main">
<block class="Magento\Catalog\Block\Product\View\Gallery" name="product.info.media.image" as="media_image" template="product/view/gallery.phtml"/>
<block class="Magento\ProductVideo\Block\Product\View\Gallery" name="product.info.media.video" after="product.info.media.image" template="product/view/gallery.phtml"/>
</container>The ProductVideo Block is the important one.