It seems that blender cant handled when Grease Pencil stroke are moved to a different layer that is already linked to a bone.
When I do that, all the other Grease pencil disappears leaving me with the moved strokes, same thing when I paste the stroke to a layer with linked bone. And I get a Unhandled ID GDGPencil
I suppose I can just move the strokes to different layer first and then link it to a bone later. But is there anyway to fix this?