Embedded content carries a full screen button instead of an open in new tab button. Hover an image in a project and you get controls for opening the original file; hover an embedded video, 3D model or board and the only control is the full screen icon. Nothing is broken and nothing is missing for your account.
Full screen goes to the frame itself
Selecting it hands the embed to your browser at the size of your whole screen, which is the intended way to look closely at a model or a plan. Escape leaves it. The provider's own controls, play, pause, orbit, zoom, live inside the frame and behave exactly as they did.
Clicking beside the frame opens the source
The area immediately around an embed is a link. Selecting it reads the address out of the embed and opens that address at the provider in a new tab. It reads like an accidental navigation the first time it happens, but it is deliberate, and it is the way to reach the original when full screen is not enough.
Clicks inside the frame belong to the provider, so where you click decides what happens.
Why images and embeds differ
An image on UNI is a file we hold, so there is an original to open. An embed is a window onto somebody else's site: we store only the code, and the file behind it stays with YouTube, Vimeo, Sketchfab, Figma or whoever hosts it. There is no UNI address to open, which is why the button is absent rather than disabled.
If the frame is empty rather than showing content
That is a different problem. The embed saved correctly and the provider is refusing to display it inside another site, usually because the content is private or the wrong kind of address was pasted. See Which embeds you can use in a project.
Signed out, the whole media block is replaced by a sign in card, so no controls appear at all. See Which parts of a project page disappear.