Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce GTX 750 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 456.71
Broken: version: 2.91.0, branch: master, commit date: 2020-11-25 08:34, hash: rB0f45cab862b8
Worked: (newest version of Blender that worked as expected)
Short description of error
When using the tools meant to constrain the rotation of bones involved in the IK chain it seems to only apply to the first one. In the example file bone 2 has lock IK X,Y, and Z as well as the limit rotation contraints for X,Y, and Z for good measure. Bone 2 is the one with the IK chain of 2 applied and bone 1 is clearly effected but with the limits and locks applied it shouldn't be moving at all and yet it does.
Exact steps for others to reproduce the error
see that IK locks are applied to bone 1, move the Target bone around and observe that indeed the locks are not being applied.