Operating system: Windows-8.1-6.3.9600 64 Bits
Graphics card: GeForce GT 730/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 441.12
Broken: version: 2.81 (sub 16), branch: master, commit date: 2019-11-20 14:27, hash: rB26bd5ebd42e3
Short description of error
When I add multiple ITaSC IK to the bone chain they doesn't work (moving IK target have no effect) if bones were created in order that is different from parenting order
Exact steps for others to reproduce the error
Inside the Top Armature I added single bone then subdivided it, then rearranged endpoints and added IK targets (blue) and IK constraints. Both IK work on this armature.
I created Bottom Armature duplicating Top Armature. Then I deleted Bone.002 and recreated it, then added IK constraint on bone Bone.002 again. While Top and Bottom armatures looks same and bones have same parenting order, both IK on Bottom Armature stop working.