Defliers i placed are not burrowed on map. They are owned by p12 and properties are burrowed and invincible. WTH?
You need the burrow ability to be researched. It goes for all burrowable units except lurkers. If it is not researched they won't burrow.
or if you dont want to make burrowing auotmaticly researched you could switch the defiler with a hero defiler so it already has burrowing.