Kinda ironic

Fitting for a series all about genetic memories to have a serious bug like this - with the new Hidden Secrets DLC, Assassin's Creed III players are finding their mission progress on some quests completely erased. Ubisoft has acknowledged the bug, and they have said they have reproduced it and are working on a fix. 

As for now, they have recommended all players to avoid loading AC3 while the DLC is downloading, which appears to be the trigger that is starting this bug. 

Julian "Mirai" Williams