This one too? Amazonia does the same. CRAPPY ♥♥♥♥...

Not a bug. That's the game's default. The devs never made that part of the texture, since their version forces underwear to appear and cover the holes... even though the game says your character spawns "naked" on a beach.

This mod simply patches those omissions when you apply the matching skin to your chest armor and pants, and makes the default underwear invisible. Wear armor with the skins applied, then unequip the armor, and the holes will be gone.