It is addressed on UESP.com
If you kill Eola in Namira's quest INSIDE markarth tombs, brother verulus will reward you with an amulet of arkay and a permanent glitch. This glitch is the fact he freaking follows you everywhere and attempts to talk to you. And he is essential too! He follows me everywhere attempting to talk to me and i had to roll back a couple of saves just to not attempt namira's quest. How do you fix this?

I am on PC btw. Kill commands dont work since he is essential.

In my game he is stopping me each time with "dialogues" and I get mad to escape it each time. I try to avoid him but he is standing right on my way. At least I can manage this glitch..