I also had issues with scripts not working in a duel map under 3.1j EE (and even under the RPE-based EE), and in the duels themselves, there were no elemental effects on the creatures of the Academy for Erin, and the enhanced slowing cold spell didn't trigger with luck, which, as is known, was fixed in patch 3.1. Something Quantomas isn't telling us...

This is an unofficial build, so the error might be due to that.

This isn't just any build; it's the Eternal Essence mod.
I searched through Heroescommunity, and in the EE forum, it says that some resources were taken from 3.1, and some from 3.0, which is why these script issues are popping up. It's like they're trying to fix them, but I don't remember when the last update was. But, like, Quantomas didn't promise anything to anyone...