Hi, I've got a strange issue with my game.

When i use dead thrall on an ancient vampire, while having serana as a companion (for dawnguard questline), serana and the ancient vampire randomly start fighting. I don't have a red marker that indicate an ennemy when looking at the ancient vampire, but her spells hurt me. However, it doesn't seem hostile to me.

While i enjoy the serana/ancient vampirette catfight for my attention, i don't know what causes it.

Is this a known issue? Does someone have a similar experience with this spell and serana?

Thanks !