Also related to the new mercs:

When you have any of the natives hired, one can no longer shop from shopkeepers. When opening the buy/repair/whatever menu, the game builds a list of all their 33faces. As the natives do not have such faces, the game receives an error and aborts opening the menu.

Fix will be easy: simply add those pictures.

Morale of the story: When adding new faces, add all faces, not just some.