In addition to the original bug report, I've gone through cleaning up a range of related bugs which only became clear when hunting around the code... * Custom Handle References weren't getting cleared when the bones they used got deleted. But, neither was the custom bone shape location/transform reference. * Various places where posebone settings are copied around were also missing code to handle the new Bendy Bone properties. (WHY DO WE HAVE SO MANY VARIATIONS OF COPYING POSE DATA!?!?) * If duplicating a Bendy Bone with custom references, and the custom references are also selected/duplicated, the new Bendy Bones will use the corresponding duplicated bones