[Sicaire]

I have had the same "bug" happen to me in an 3.17 MP game with CB 1.21 and single age mod.
I had a golem carrying just the 2 astral gems needed and returning scripted as first action. He got attacked along with 3 or 4 PD by 3 enemy illusionists and ignored the scripted cast returning spell.
I would have said it was because the adverse party was not deemed threatening enough by the AI to use a spell involving a gem cost. The AI commonly ignores gems costing spells in scripts if the enemy army is too small. Problem: the golem got lighted and died with a horribly costly gear of magic items doh...