How to tell what wake source is when Wake Source: Unknown

I think I finally found out how to tell what the wake source is in this scenario:

Get-ScheduledTask | where {$_.settings.waketorun}

This shows the "Reboot" task under UpdateOrchestrator which I believe might have been causing the problem.

Instructions on how to disable it are found in Step 2 of this fantastic answer: https://superuser.com/a/973029/226996

I'll report back if I'm finding the computer is still waking and I can't determine the source with this method...

I also had the issue of an unknown wake source, but I saw from the Windows System log that right after sleep was aborted (Power-Troubleshooter entry) the next event involved the Ethernet adapter that was connected to the LAN. Turning of the adapter power triggering stopped the issue, and then turning it back on but restricting the wake action to magic packets solved the issue. Not sure why the cmd for lastwake couldn't reveal this, but it might be helpful to others.