I get the CTD as soon as I click the arrow after selecting faction. This is on vanilla RTW, but all land pixels in map heights are greyscale anyway. Map features is all black (RGB 0, 0, 0), and all colours are accounted for in map regions I think.

A jpg version of map heights is in the 1st post of this thread. Otherwise, which files do you want to have a look at? I'm only following a tutorial making this, so I don't see any reason to keep it totally private.