So the area which activates the Brute is called brutey, the area in which the Brute walks is called brute_go. Check if the names are the same in the editor and make sure the areas are big enough.
Not sure if SetEnemyDisableTriggers("Brute", true); disables interaction with areas too.
You may try to add SetEnemyDisableTriggers("Brute", false); to "unlockdoor".
void unlockdoor(string &in asItem, string &in asEntity)
{
SetSwingDoorLocked("unlock", false, true);
PlaySoundAtEntity("", "unlock_door.snt", "unlock", 0, false);
RemoveItem("key");
AddEntityCollideCallback("Brute", "brute_go", "Monsterdisappear", true, 1);
SetEnemyDisableTriggers("Brute", false);
}