Magenta shift/Blue Hue You are right on.
Their color engine I suspect. Somewhat common years ago, not quite as common today. You'll see very little of this with the i1Prism color engine.
I have a very good synthetic test file for this built by Bill Atkinsion (Bills 23 Balls). Used to be up on his site but no longer. I don't think he'd mind if anyone wants a copy, it's just awesome for finding out color engine issues like this: