A hotfix was patched to the servers this morning. From the patcher:

*** Hotfix ***

- The Unburrowing - No adds will spawn once the Protauris starts attacking.

- The Unburrowing - Added more time between when the Magrix attack and the Protauris attacks.

- The Unburrowing - Added 5 minutes to the time that must pass before the Protauris increases his damage.