Hi there! I understand you're having trouble stopping audio playback in the Chirp Audiobooks app on your Mac running OS X 10.15.7. Let's see if we can get this sorted out for you.

First, can you tell me a bit more about what happens when you try to stop the audio? For example, does tapping the pause or stop button not respond at all, or does the audio stop briefly and then resume? Also, are you using the Chirp app downloaded on your Mac or listening through the web browser?

In the meantime, here are some general steps you can try to address the issue:

1. Update the Chirp app: Make sure your Chirp app is the latest version. Sometimes playback issues happen with outdated software.

2. Force quit and restart the app: Close the Chirp app completely and reopen it to see if that resets the playback controls.

3. Restart your Mac: This can often clear minor glitches affecting audio playback.

4. Check for conflicting audio apps: Ensure no other apps are controlling audio output as this can interfere with stopping playback.

5. Clear app cache or reinstall: If possible, try clearing the Chirp app cache or uninstalling and reinstalling the app to remove corrupted files.

If these don't help and the stop function remains unresponsive, please let me know exactly how the app behaves when you attempt to stop the audio. I can then guide you with some more advanced troubleshooting or help escalate the issue if needed. How does that sound?