I'm having this issue too but the solution didn't work for me.

Yes, they do! If I create a new SwiftUI project, and copy the same files over it works.

Did you ever get clarification?

I've also tried to remove the audio from QuickTime and export a new video, but I still get this error message. Any ideas what the problem could be?

I have this same problem sometimes with my 2018 MacBook Pro. I've never found a solution other than restarting my computer. It happens sometimes for me if I'm listening to music and also running Xcode with the simulator.