I know this is completely redundant after so long, but the file was just a symptom of working in a Linux distro if I remember correctly. Had nothing to do with the mod itself.
Using GIMP, it asks some question that needs to have the box unchecked. Although GIMP 2.10 knows to orient the option from bottom-left, you're supposed to uncheck the box.
As far as why this happens/what it is, not entirely sure. I never needed to know too much about it while using GIMP with KotOR or TSL.