OS 25 Shadron/Tenebron Exploit - Shadron not spawning.

[Dismay]

Yesterday when i did a PUG for OS 3d, we all snuck around the walls to kill the trash but on Shadron we accidentally aggroed him. We all successfully got out, and came back in. We noticed Shadron wasn't there anymore. We though hmm.. wierd. But went on. While fighting Sartharion we noticed when Tenebron, or the first dragon shes supposed to send in.. didnt come... I don't know if this is a bug or not but i thought it would be helpful to the MMOwned community.
Thanks!
-Dismay
Edit: Sartharion also casted (Saw on DBM) or not casted but i saw on DBM that it would spawn. Just if you were wondering!

[Omgroflnocdhack]

this happend to my group too actually we were all like hmm :P