Rejected Boss stuck in the World

Bug Name:

Boss stuck in the World​

Bug Description:

Quests:
Quest name - [Boss]Muskan of Madness
Step that is bugged - Defeat summoned Muskan
What is bugged with that step - The boss is forever stuck in a rock

Items:
Item Name - Monastery Boss Summon scroll
What the item is supposed to do Summon Muskan for Black spirit quest
What happens when the item is used - "The Monster which has already been summoned" pops up and nothing happens
i.e. Status Change Icon Appears (include what status is supposed to happen).​

How to reproduce/proof:

When I summoned the boss for the quest, During the cutscene he locked on to my party member and ran off screen in the nearby rock, I have not been able to finish the quest nor can i summon any bosses on any other character http://imgur.com/a/KvTqf​