iMovie and incorrect "Storage Full" error

I am running iOS 14 on multiple current devices (iPhones, iPads), and they are ALL experiencing the same problem.

I have a 750MB mp4 movie that I have edited in iMovie, Splice, and other video editing apps. NONE of these apps will allow me to save the movie...at all, on any device. Not to Files, Dropbox...anywhere. This applies to any other video file of the same size, or larger.

I receive the same error: "device storage is full or almost full"....despite having at least 40GB free on every device and iCloud.

Solution? Suggestions?

So maddening!

Thank You.