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

I noticed that when I took the spell "Summon Creature VIII" I was no longer able to summon from the Greater Planar Binding list when I go to use Contingent Summoning from the Thaumaturge abilities. Is there anyway to change this? They are both lvl 8 spells. Is the Summoning creature 8 a stronger spell and that's why it's having me summon from that list?

Not a bug.

Summon Creature trumps all others.

It just is what it is.

If you do not want to summon creature with contingent summoning then you have to ensure you do not have summon VIII or summon IX in your spellbook at all.