If you have a tamed llama with a carpet and/or chest in its inventory, when a wandering trader walks by with his pair of llamas, the player tamed llamas will attempt to join his caravan unless you use leads to attach them to a fence post or something.
This does not seem like intended or desirable behavior.
There was a similar fix where trader llamas wouldn't join normal llama caravans ins some cases (MC-143412), suggesting that this behaviour is intended.