Cartographer Villagers never unlock item frames

I have tried numerous times with many many villagers to get a Cartographer villager that trades item frames. Honestly the only reason that I want the villagers in the first place. But unfortunately no matter how many villagers I cycle through and kill. They always unlock 2 banner trades, rather than 1 banner trade and 1 item frame. I do realize that they are supposed to be random, but not every villager I go through should always have banners, there has got to be some item frame ones. Telling me that the game is bugged.