Little bit of an update:
Turns out that adding another "_enemyAction[1]" to the line below in the create event of oBattle allowed me to complete the second battle, and then the game crashed on the third battle, not sure if it's a fluke or not:
//run AI script for that enemy
var _enemyAction = _unit.AIscript();
if (_enemyAction != -1) BeginAction(_unit.id, _enemyAction[0], _enemyAction[1], _enemyAction[1]);
Normally it would look like this:
//run AI script for that enemy
var _enemyAction = _unit.AIscript();
if (_enemyAction != -1) BeginAction(_unit.id, _enemyAction[0], _enemyAction[1]);
Hopefully this is helpful!