Just to confirm it was not just the M4 and V4 figures, I tried the same test with M2 and V1, which again share material names.  Same result.  If the material names are the same, it seems that whichever figure is listed first in the materials display is the one who's textures get used for both figures after the swap.

I have the zip file generated and am looking for a place to put it.  I'll send you a separate email when I have that.