Line 241-243 of maps.py:
for i in range(3):
vertex_id_int = triangle_m_int_array[i]
You mentioned "current model topology", so I'm assuming you've retopologized. So based on that, and based on my experience with weights, lists and encountering "list index out of range"... if I'm not mistaken, zivaSave/Load requires the same objects to have the same topology at the time it was saved, for it to load correctly. You can do things like SCULPT or edit your JOINT-RIG, but retopologizing is too structurally-fundamental of a change on the mesh-side of things. This is common for many tools/functions, such as for working with blendshapes, xGen; not just for Ziva. (I mean, I'm nowhere near the greatest programmer, but the code essentially states that the data was stored based on a list... and by adding or removing topology, you're altering that list for which the data-stored depends upon, which messes things up.)
IME, you can either see what you can get away with, with your previous topology... or you have to rebuild.
Or more specifically, you can restart from your previous working topology, and then just removeZivaTissue on L_Achilles and then redo the attachments/settings with your L_Achilles_new; thus preserving most of everything else.
It is just the nature of meshes/topology/retopologizing.