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.

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?

Did you ever get clarification?

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

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