Two recurring issues with QuickTime Player. I use it to convert YouTube videos to audio.
1. It lets you pick a filename that’s too long and then just fails instead of warning you or auto-truncating.
2. After it fails, you can’t immediately retry. The Export command is disabled because the progress window was made frontmost, and I guess the app allows it to become main instead of just key so it no longer knows what the frontmost document is.