I think maybe the Chasers aren't being reset when their alertcooldown reaches 0. In event 5 you have a trigger once that won't work well with multiple objects. Say you have two chasers with alertcooldown > 0. When one of them reaches 0 then event 5 runs and sets alerted to false. When the second chaser reaches 0 that event won't run again, it already "triggered once" so the second chaser doesn't get reset.
Events 5 and 10 do the same thing right? I'd say try getting rid of event 5 and remove the trigger once from event 10 and see if that helps.