I recall having a similar issue. Do you know what the trigger for it is? Or what you were doing before he gets to you?
The being unable to run is normal. It happened to me when having conversations with multiple NPCs. I don't have a technical way to prevent it but I was able to side step it by waiting for him to get close then start a multi NPC conversation with Darian included. Also maybe gift someone the pendent and get a different one.