Game breaking bug Mastodon Tusks doesnt drop

On my second Char the Mastodon Tusk doesnt drop even after doing the Boss 5 Times and resetting the Map it just doesnt drop. It Tells me to go to the Bone Pit and than to recieve the Tusk and I think normaly it would tell me to find the Boss location and kill them for the Mastodon Tusk but that doesnt happen and it never drops. Any Idea how to fix that because I cant progress without the Item ^^