Is it just me or do bombard cannons not listen to my orders?

So my favorite civs and unit are the Turk/Italians (don't judge me) and the bombard cannon.

Naturally, I create a fuckton of BBCs to take down castles and such, but whenever I make them target a building, most of the BBCs just decide to... Walk around while only one actually shoots what was targeted.

How can I make them actually do what they're ordered to?