In the Underworld's last Battle- Number of the Beast, on level hard- I am unable to fulfill the "Survive with 1 allies" objective. Every win I survive with both allies, one of them occasionally will have the stunned circles whirling around their head but they are still active, not sure if this bug effects it but regardless I still have one ally that is perfectly fine.

Does anyone know how to beat this? Really hoping to unlock the secret location on this level and this bug is the only thing preventing this. Thank you!