iMovie project won't finalize after sharing

I've just finished an iMovie project; I 'shared' it & have played it from the Finder window so I know it's finalized. I can also see it in the 'Projects' window in iMovie. However when I click on it in iMovie, it shows me the 'in progress' window - with the movie in segments & all the media at the top, as if I'm still working on it. Please see the screenshot. But it's completely finished! How do I actually get it properly finalized in iMovie, so it goes away from this window, and how do I get rid of all those media clips? I tried deleting the media clips but it said that they were 'still in use', so clearly it thinks the project is not finished.

Please can someone help? This is so stupidly basic, and I've made tons of movies in iMovie and this has never happened before - normally after I've shared it, the movie goes away to the projects sections and vanishes from the 'working' window.

I'm using a Macbook Air, running Sequoia 15.7.3.