IK not working properly I did the exact same IK steps in two armatures and one of them SimpleArmature works great, but with the second one HumanArmatureit works really bad. Each of them has an IK bone named "IK" which should control the left Arm of each armature. With the HumanArmature once I grab the IK bone I find it flickering and rotating and it's very hard to control. I don't know why and how I can have a better IK control in my HumanArmature

My blend file can be found here in this link.
It's a circular dependency: the Ik bone is moving the forearm, which is moving the ik bone, ........

Select your armature, go to edit mode and unparent the ik bone from the forearm. Then you can parent it to another bone which is not part of the IK chain.