Error putting character in walking scene

I vaguely remember a similar error a few years back (so might not be related). It happened when the handle for something was not inside the artwork, so it go confused. But i would suggest using puppet export from the menu in case the adobe folks want to debug it. But can you share a screenshot of the rigging hierarchy? If you want to use the walk cycle, you will probably need to add tags for everything (including waiste and neck). The relative positioning is important to Ch. There is also a 'warnings" panel you can expand that reports common rigging problems (beneath the character artwork in rig mode). It might give a hint.

But that sort of error is an indication of a bug. The question is can you fix some problem in the puppet and make the error go away. The rigging hierarchy is the most useful for debugging those problems (or share the exported puppet)