Baldur's Gate : The Sword Coast Chronicles : NWN2 Persistent World

While in the underground ruins at East Wyrms crossing, myself and my companion caused a boss mob to spawn. We each attempted to summons creatures to help deal with them. No creatures were conjured despite casting;

Summon creature 7 Scroll
Sand warriors
2x Animate dead scrolls (Feedback from combat log stated 1 and 4 were raised)
2x Summons Creature 1
2x Summons Creature 4

This is not the first time summons have failed after boss mobs arrive, it is however the most obvious example of it.

Edit: Leaving, resting and returning seemed to allow summons to work once more while the boss spawn was there. No idea why.

Just as a followup to this...

Seems to happen in the near vicinity of any boss enemy. Being some distance away and summoning works fine.

So it makes me wonder if bosses are equipped with some sort of suppression aura.

In an effort to temporarily suppress additional enemy spawns, I also accidentally suppressed spawning of the spell node that handles summons. This should be fixed after next update.