My AI share the same Behaviour Tree and it's a mess.

So, my shooting NPC characters share the same AI Controller, Blackboard and Behaviour Tree. It works fine, in case there is only one NPC. But, should you add another one, and it turns into a bloody mess. Simply saying, their response is inappropriate. If I’ve been seen, NPC should open fire. If I hide behind the wall, AI should stop firing, move to cover and when visual is restored, start firing. And it does so if there’s one NPC. After adding another one, it keeps firing even when I behind the wall. Every variable in the blackboard has this “Instance Synced” ticked. I don’t know what else I can do to make it work. Could use some help.