I have had the same results so far, Mission never actually completes. I suspect that it's due to the fact I have been killed each time in the explosion at the end. I get the items from the kill and the message that all objectives are done but it never actually completes.
Slowed it by teaming with a friend and let him drag me around the mission.
Thanks for the "help" PWE. Looks like your ticket system works just as well here as in Perfect world and Jade empire. Over a week with no reply
I got stuck in the same loop, i did the mission twice and it kept starting over then i made a ticket
But being impatient as I am I managed to figure it out
When you enter Donia, regardless of the fact that you clicked Begin Doomsday Device it for some reason was starting a patrol Donia mission with it, this seemed to cause a problem because it made the patrol primary
I dropped the patrol mission and the Doomsday machine mission finished properly