Concat error in spawn transform control?

I’m new to rigging in Unreal Engine, so I don’t know exactly if this is a bug or not.
When I use the Spawn transform control in the Control Rig Blueprint to create controls, if I leave the Name in the For Each node unchanged, it creates controls or nulls like the existing bone hierarchy, but if I use a Concat on the Name to give it a custom name, it breaks all the existing bone hierarchy. Is this a bug? If it’s not a bug, I’d like to know how I can restore all the existing hierarchies or how I can rename the controls using concat again after their names.