We tried killing Klaus but then Deerclops spawned and you probably figured out what happened next. We didn't wanna fight Enraged Klaus and we didn't wanna despawn him and come back, so we just rollbacked. We came back, put the Antler in, and nothing. The character said the quote ("Either the key is wrong, or the lock is"), and it did drop a Bone Shard. We looked around, no Klaus in sight, no epic boss music. My brother got another key and tried it again, same thing. A quote ("Blast! Wrong key.") and a bone shard, but still no Klaus and or epic boss music. I pretty sure he didn't spawn entirely, because we searched quite a large radius around the Loot Stash. Nothing. I think the rollback might have something to do with it.
Ok, I am back with day 2 of this bug, and I think I have traced down the source of this problem. The problem persisted, and Klaus would not spawn, so we assumed that maybe since we already had a Stag Antler in the world, for cool collection, but then we remembered it worked yesterday. We decided to delete the current stash and respawn it with a new one. Surely enough, it worked and Klaus spawned as normal.
I think that if Klaus for some reason the Klaus linked to that stash refused to spawn, somehow by rollback or something else, and spawning a new stash fixed the problem. I think it might have something to do with the new changes to Loot Stash drops, that being you can't rollback to change them.
1. Activate Klaus fight.
3. Return to stash and try activating the fight again.
4. Wait for eternity....