This happened on PS last night during the last 30 minutes before server maintenance.
We grouped up, queued and completed Castle Thorn, killed everything possible, did hard mode, and did not die but no achievement at the end. We have saved video clips of it all available. We did have to restart after two failed attempts and we just queued for the dungeon again each time. One instance of queuing seemed to "kick" a member out and sent them back to the pre-dungeon zone that they were in but the rest of us were put into a new Castle Thorn instance and the last person had to travel to the dungeon to do the run with us. This last oddball group queue was when we did the speed, no death, hard mode but did not get the achievements. I submitted a ticket but have not heard back yet. Has anyone else experienced something similar?