Fleece is supposed to start with pick lock skill and Prima's Guide to the game says that skill needs to be maxed. I have missed picking up a lot of "packages/bags" in several random world map locations as well as Lenele palace, Khomani, and now in Ikaemos palace. I've tried solo'ing Fleece (she's the only one with this skill) but nothing works with GOG Galaxy version of the game. I played this game 20 years ago on my PC, it worked then. Why doesn't your version work?

It works perfectly fine. You have to use it from your skill list or quickbar.