Why can't commanders follow scripted orders?!

[ArkhanTheBlack]

I'm not sure if this is a bug, but in my games it happens regularly that a commander / pretender doesn't follow his scripted orders. It usually starts with the commander casting astral shield for no obvious reason because it was never scripted. Then it's possible that the right spells follow in various orders or they just attack. I'd say it happens with my pretender in about every 5th battle. Against low or mid strength opponents it's usually not so dramatic, but against large armies with some nasties it's pretty much a death sentence.
The annoying thing is that this problem is the default reason why my pretender dies. And in critical situations against higher difficulty AIs I can loose the whole game because of that. Am I the only one who has this problem?