Darkness seems to be performing differently

[Philly]

Although I don't venture out nearly as much as I used to, my wizard character relies on darkness because he cannot cast illusion spells.

Before, when things were turning south, I could cast darkness, heal my summon, and let him loose again. Or, keep in the cloak of darkness with ultravision and get some great concealment.

If the summon died, I would typically greater sanctuary, then cast darkness where I could create a new summon and buff him before sending him back out.

Now, it seems like darkness completely ignores my summon. I have tried all sorts of combinations...summoning inside darkness, casting darkness on top of a summon, controlling my summon to run into an already cast darkness...it doesn't seem to matter. No matter what, every hostile npc will attack my summon as if darkness didn't exist. They don't have ultravision or anything either, because they ignore my pc.

Is this a bug, or is this the intended performance for the spell?

[Biolab00]

Did you cast the darkness spell too close together?
The spell itself cannot stack

Hence, if you casted it the 2 darkness spell directly beside each other, the 2nd darkness spell is as good as not being registered to the NPCs monster. Hence, they will totally ignore it.