How are you triggering the crash? After some experimenting we found that opening spineboy-mesh.spine and moving the hoverboard bone under the front_shin bone caused the crash. However, this move is invalid because hoverboard has a child bone front_ankle_ik which is the target of IK constraint front_ankle_ik which controls bones front_thigh and front_shin. If that was confusing, try this (simplified from the actual project slightly):
IK constraint:
front_ankle_ik
Parent: front_thigh
Child: front_shin
Target: front_ankle_ik
Bones:
front_thigh <- IK parent
front_shin <- IK child
hoverboard
front_ankle_ik <- IK target
Result after move:
front_thigh <- IK parent
front_shin <- IK child
hoverboard
front_ankle_ik <- IK target
This is invalid because the target cannot be a child of the IK bones. I assume you are doing a similar invalid move? Spine should not crash of course and we will fix this in 3.0.09. It should not be possible to choose invalid parents (we already disallow similar moves, but missed this type). Thanks for posting the error!
