How do I make a vanilla unit available to factions that don't normally have it?

[Thunderbolt II]

For example, I tried to add African Elephants to Meroe, Axum, and Blemyes. I edited the tables for custom battles and the campaign. But when I tried to load the game, it just kept loading. I had to restart my computer to get out of it. I have prefixes for all my DB tables. Does it have something to do with overriding the vanilla units? .

[Karnil Vark Khaitan]

For custom battle you edit:
unit_custom_battle_permissions
For Campaign you edit:
units_to_groupings_military_permissions

Remember to give it a nickname in front like:
nickname_units_to_groupings_military_permissions

So it doesn't overwrite, there is no need for that, if I got you right.