Can't export file from iMovie.app on Mac

UPDATE: Just updating iMovie was apparently not enough. Somewhere along the line MacOS had downloaded but not installed a software update and allowing _that_ to install was apparently the secret sauce to getting the app and the frameworks in synch again. After the OS was _also_ updated, encoding worked better.

It's odd that encoding worked before the iMovie update then broke until the OS update. I thought part of the point of having frameworks that could be embedded into apps and object oriented software that inherited improvements as they became available was that you didn't end up with the equivalent of DLLs out of synch with apps and the like, because the app you launched always linked at runtime with the frameworks and services that supported it. It might be worth warning people against software versions that require an OS update to function as expected, so people can plan accordingly: lots of folks get treed with an OS version they can't update due to software that breaks on update, so warnings about software from which one can't downgrade to a working version would be valuable to users.