My Duo 2 received the June update yesterday, and since I haven’t had any more issues with my device restarting randomly while connected to wi-fi. Microsoft has even confirmed the fix in the release notes that were updated today.

Release notes for Duo 2: https://support.microsoft.com/en-us/surface/surface-duo-2-update-history-a3e72e49-8165-4ea6-b490-7fdc2a76c262