Pawn unable to wear pants

My pawn is unable to wear these flak pants I made because "would replace locked apparel." What does that mean? Also, this pawn is able to wear any other pants, just not flak for whatever reason. And, other pawns in the same ideology can wear the same flak pants.

https://preview.redd.it/krf17vwpiqyf1.png?width=1863&format=png&auto=webp&s=0cb888d727f1925f0d44de0c4cea1710b2a4a589