Bug with HumanIK: Baking joint animation to control rig, joints disappear

[komorebi44]

Hello,

I have the following problem and it's been driving me crazy:

I have an animation on the joints/bones of a rigged character that's using HumanIK (characterized Unreal rig, referenced from the rig file) and bake it to the Human IK control rig.

The first issue (Video 00:00:41): Some joints will turn invisible. Their visibility in ChannelBox is 'on', they're shown in the outliner and the animation still looks correct, even when switching the source back to skeletal animation. I can still select them in the outliner and rotate them around and the skin will behave correctly.

They're still invisible after exporting the joint hierarchy (root selected) as an fbx and imported again in a new Maya scene.

The second and more pressing issue (Video 00:01:40) (that might be related to this): When the animation is baked to the control rig and then baked again to the skeleton, the source does not switch from 'control rig' to 'none' as it is supposed to.
This means that when I want to bake my skeleton animation back to the control rig, I don't have the option 'Bake TO control rig'. I only have the option 'Bake Control Rig'. So whatever changes I do in my skeleton animation will not transfer to the control rig as it only bakes the rig onto itself again.

This means I'm unable to switch freely between skeleton and control rig animating, which is very frustrating as some things just work better on one or the other.

I was able to (re-)create the problem with Maya 2023 and Maya 2024.

Could be important:

- I have a naming issue, the right lower arm is 'lowerarm_r', the left I made a naming error, it's called 'lowerarm_'

- I have tested another rig (also characterized with HumanIK), the bones also disappear when baking to control rig, but re-appear when  baking back to skeleton, so maybe rig related?

- The error message that appears when baking from control rig to skeleton:

"Error: file: C:/Program Files/Autodesk/Maya2024/scripts/others/hikSkeletonUtils.mel line 182: Cannot delete 'FemaleWorker_RIG:pairBlend1' as it has locked or read-only children.", repeats until RIG:pairBlend52

What could cause Maya to make this mistake? Is it checking for correct naming?

Why do the bones turn invisible even with another rig (with correct naming)?
Is it because I'm using a referenced rig and the pairBlend nodes are thus locked / read-only?