This bug has been present for awhile -- 2015, I suppose -- but I'll go ahead and throw it out there.
Spain uses the usmolle infantry model and the sim looks for a usmolle.dds skin to cover it.
But the default skins in the "es" camo folders are of the interceptordress pattern (body armor with groin protector; nightvision mount) and have the interceptordress.dds filename, so they are ignored.
The (unmodded) sim then defaults all the way to the base season folder, where it finds a USMOLLE.dds skin, which is ... wait for it ... the same skin as the interceptordress skin in the es nation folders.
The result is a skin that doesn't quite fit the model.