Running with --video where the video would need to be overwritten silently stalls browsertime (macOS)

When running a test where the video recording already exists (and would need to be overwritten), I'm seeing browsertime silently stall after issuing the ffmpeg video command. (macOS).

If I delete the previously-made video, the new recording will be made and the test will proceed.

For instance, here's an example ffmpeg command:

[2021-04-30 16:25:37] DEBUG: [browsertime.video] Start FFMPEG with ["-f","avfoundation","-i","2","-r",30,"-filter:v","crop=2732:1536:0:0","-codec:v","libx264rgb","-threads",0,"-crf","0","-preset","ultrafast","/Users/acreskey/tools/browsertime/responsiveness/browsertime-results/facebook/firefox/x11-tmp.mp4"]

If I run that from the terminal, I see the prompt: Overwrite ? [y/N]

It looks like adding the ffmpeg option, -y will force an overwrite.
@dpalmeiro, who helped me debug this, raised the possibility that a timeout could be added.

Here's my browsertime command:

./browsertime/bin/browsertime.js --skipHar --videoParams.addTimer false --videoParams.createFilmstrip false --videoParams.framerate 60 --video true --visualMetrics true  --firefox.windowRecorder false --visualMetricsContentful -n 1  --verbose --resultDir  browsertime-results/facebook/firefox -b firefox tests/facebook.js

Where the test is simply:

module.exports = async function(context, commands) {
return commands.measure.start('https://www.facebook.com/');
}