Can't change my followers into vampire lords with amazing follower tweaks

[ShiroKeisuke]

I know it's a little bit late but I cant turn my followers into vampire lords. I know there's an option to change them into vampire lords and I changed them but when they change, they don't appear. Only clothes appear without the body. After that, they change into human form again. When I tell them to change into vampire lord again for 2nd time, they change and disappear completely. Even the clothes. They are still there and I can hear their voice but I don't know where they are. So, I cant even interact with them anymore. Anyone having this problem? Or is there a way to fix this?