More info

Entering the area on foot from any direction none of the savanna creatures spawn (other than the elk and one tiger)

Wonky workaround – If the player exits the game in the savanna then reloads the game the Rhino, Elephants, and Thunderfoot will spawn. If the player leaves the area and comes back they despawn and wont respawn.

The lion ( the one that usually sits on the rock in the center) still never respawns and I havent seen any of the mini boss savanna cats spawn at all.

I think the elephants and rhino are one bug and the cats are another unrelated bug.