Hi there! I understand you're experiencing crashes with the YouTube Music app specifically when trying to download music as a Premium user. That definitely shouldn't happen, and I'd love to help get this sorted for you.

To start, could you please confirm a couple of things for me? Since you're using a WebKit-based browser on Windows 10, are you accessing YouTube Music through your web browser or a dedicated app? Also, do the crashes happen immediately when you try to download a song, or during playback of downloaded music? Any extra details on what exactly happens (error messages, how the app crashes) would help.

Meanwhile, here are some general steps you can try to resolve crashing issues related to downloads on YouTube Music's web experience:

1. Clear your browser cache and cookies: Sometimes corrupted cache can cause instability. In your browser settings, clear browsing data, including cached images/files and cookies, then restart the browser.

2. Check browser updates: Ensure your WebKit browser is running the latest version for compatibility fixes.

3. Disable browser extensions: Some extensions might interfere with downloading or playback. Try opening YouTube Music in an incognito/private window or temporarily disable extensions to test.

4. Sign out and sign back in: Occasionally, account session glitches can occur. Sign out of YouTube Music and sign back in to refresh your session.

5. Check storage and permissions: On Windows, ensure your browser has permission to download files and sufficient storage available.

If you've tried these and the problem persists, there might be a deeper issue linked to how offline downloads are managed on your device setup. Sharing any error codes or specific behaviors you see during the crash will help me find a targeted fix.

Let me know what you find out or if you want me to guide you through these steps! Are you satisfied with this initial guidance?