Third Party Network Animator not syncing - Mirror Networking

I have a character whose Animator and Network Animator are set after instantiation by the network manager in this function

Code (CSharp):

1. public void ReplacePlayer(NetworkConnectionToClient conn, uint characterID, bool keepPosition)
2.     {
3.         GameObject oldPlayer = conn.identity.gameObject;
4.         CharacterSelect selectedCharacter = GetCharacterByID(characterID);
5.  
6.         GameObject newPlayer = selectedCharacter.GetController();
7.         NetworkServer.ReplacePlayerForConnection(conn, Instantiate(newPlayer), false);
8.  
9.         conn.identity.GetComponent<AnimatorSync>().SetAnimatorByID(characterID);    // sets the animator and network animator
10.         if (keepPosition) conn.identity.GetComponent<NetworkTransform>().RpcTeleport(oldPlayer.transform.position);
11.  
12.         Destroy(oldPlayer, 0.1f);
13.         OnCharacterChosen(conn);
14.     }

All the animation works locally, but none of it is synced through the network. The animation is handled by the client. Here's what the components look like:

And I also get this weird error constantly when there's a player in the scene:
Thanks a lot for your help!