Mounting Officers

I followed a guide to mounting officers, and as part of it for the officer you fill in:

skeleton_horse fs_hc_swordsman
skeleton_elephant fs_forest_elephant_rider
skeleton_chariot fs_chariot_sword
skeleton_camel fs_hc_swordsman

I tried putting a Barbarian Standard Bearer on Heavy Chariots, and a Carthaginian Standard Bearer on Elephants, but when I went to start a battle the game crashed. However, the officers mounted onto horses didn't cause any problems. Could anyone help me here?