Bug found! Possibly mod incompatibility.
I got a purple box when two of my cassowary's the birds with the big blue heads went off the map. I saved got off the game. And today I loaded it back up and they are missing their bodies with a purple huge box over their entire character. This happened after I subbed these two mods but did not check them. I think they replaced their assets possibly.

Kilhn Race
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1631597972

Slither Race
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1637478086

After unsubscribing from these mods and resubbing your mod the bodies are back after loading game.