Thanks for your answer.
i have found another guy who dont use anything
so this is a game bug.
I find that this no longer happens if I disable options before entering the boss arena. With all options disabled, the cutscenes play properly and I can simply re-enable options after the fight starts.
If you do go through this and your character disappears during a boss fight you can use a Vivifier to return to your most recent Mistle without losing your Haze and then re-enter the boss arena as normal.