2.80 (sub 45), 798d2cadc307, 2019-03-04 00:30
It seems, IK counts initial axis, not current. Here the demonstration:
And little bending is not help (yes, i know how to prevent situation with TrackTo)
But there should be something like adjustable friction or plane priority, prevents such jumps and keep initial bending plane permenent if it is possible.