Rigging - Inverse Kinematics Snapping I'm confused with this, when I have the arm in my desired position (the rest position A1) the upper arm doesn't bend to meet the IK target bone, see A2.

But with the lower arm rotated in B1, when I move the IK target upwards, the arm bends to meet it, see B2.



Why is that? What can I do to fix?
According to your file, IK limits are defined. You need to unlock related axis, or set appropriate angle ranges for consistency, in order to avoid control conflicts.