I know this bug was mentioned in another thread with respect to one particular unit (I think it was Bonesplitter?), but I've started to see various sovereigns and possibly heroes also have this bug.  In a recent game, General Carrodus appears on the map as riding a horse with ANOTHER horse standing over him (basically straddling him) on his horse.  Not a comfortable riding position for General Carrodus, as his head is positioned--err, you can picture what I mean.  The bug seems to happen with heroes and sovereigns only so far.