Were Edowin's siblings in the fight with you? I killed them before the fight on my playthrough where I successfully got the Owlbear Cub to leave the cave. Whereas Edowin's siblings fought alongside me on the save file where the cub wouldn't leave he cave. So maybe that's the issue then? Other than that I can't think of anything...
I told them to leave, I went to the cave with a Speak with Animal potion on and I left the cave without killing mamma bear. Cub refuses to spawn at Goblin camp no matter what I do and I am NOT loading a save from before meeting it because it's VERY far back from where I am now.