When adding a new movie or project and a file is found to be missing I sometimes simply want to cancel the operation while I investigate. I thought that was the purpose of the Cancel button.
But it doesn't do so. Instead it continues, adding the movie with some parts missing. (They are not even the same as those using Skip all, another option I sometime use.)

Looks like a bug to me. But if so then it's been there since at least MEP 17. Yet what else could Cancel be for?
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Terry, East Grinstead, UK