Currently, sortable cloneable nested group can be moved outside of its parent group which most on the time is unexpected behavior and will definitely mess up meta boxes data. Also it's extremely difficult to sort cloneable nested groups inside their parent (which is also sortable cloneable group) because the drop placeholder is always outside of the parent.
Another similar issue is that sortable cloneable parent group can be moved inside of another parent group. Notice that all the groups mentioned are collapsible group. I didn't test if the issue occurs for non-collapsible group.
It would be great if these issues are fixed because with their current state, the sortable cloneable nested group feature is rendered unusable.
Below is the code for registering meta boxes:
https://pastebin.com/b27yAciK
Thanks,