No idea, other than something is different (but still compatible with the game) structurally in those SHPs. It may be something as simple as being an odd number of pixels wider or higher etc when the mobhack SHP code is expecting even row or column counts, say. Check the height and width of them compared to icon sizes we use perhaps?
(The Mobhack SHP code is some Delphi that a user (I cannot recollect who now) provided to me waay back in the MSDOS days as a library package and I have absolutely
no idea what it is doing internally, I just happily used it "cuz it works"!
)