Cannot set rotation of bones at or beyond an IK chain Head

Hello,

I may have encountered a bug, or I maybe do something wrong...

I have the following bone structure:

UpperArm ==> ForeArm ==> Hand ==> fingers

with an IK chain starting from UpperArm, with Hand as an IK Head.

Hand has an effector bone and IK Controller settings set to Position, with a control parameter:

I use code to change the effector bone's position, and set the IK control parameter (here IK_ArmB) to 1 when I do so. This allows me to move the arm with IK.

After moving the effector bone, I also want to use apPortrait.SetBoneRotation() on the hand or fingers.

However, if the control parameter is anything else than 0, it seems that apPortrait.SetBoneRotation() will not do anything anymore to any bone that is part of the IK chain (which seems normal) or at/beyond its Head (which seems like a bug).

So if I use IK to move the hand position, then I cannot anymore use apPortrait.SetBoneRotation() to set the rotation of the hand or its fingers (even if it the Head of after. The fingers are not part of any IK chain)