Cook process changes startup movies?!

The project had two start up movies: our logo, and the UE4 logo.

We want to add a third movie.

The movie (MP4, 1920x1080@60fps) is placed in /Game/Content/Movies, and imported.

The Project Settings… list of startup movies has the new movie added.

I select “Cook Content For Windows…” and wait for it to complete. The shows no errors, and does appear to handle the movie.

When I’ve finished the cook, I restart the editor.

Project settings now shows four startup movies listed: Our logo; UE4 logo; Our logo; UE4 logo.