Maintenance for the week of April 6:
• [COMPLETE] ESO Store and Account System for maintenance – April 8, 9:00AM EDT (13:00 UTC) - 6:00PM EDT (22:00 UTC)
I'm not sure of the specific quests that were bugged so that they would not let you finish all areas of Shadowfen. Did this patch address those quests?
ZOS reduced the total required for the achievement to 51; that said, the patch caused me to reset from 60/62 to 0/51. In fact, all my area/zone-based quests reset to 0 and I lost all my associated achievement points.