Breeding Trader Llamas doesn't work

I have tried breeding two Trader Llamas together (three separate pairs) three times now, each time resulting in no offspring and a tiny amount of EXP, and nothing else. As this has happened three times now, I decided to use a spawn egg to compensate myself, and just give myself the babies as I didn't want to skip the time it takes for them to grow. When using the Egg on the Trader Llama, it would spawn a baby Trader Llama, and then immediately despawn it. However, when simply spawning a new Trader Llama as normal, I ended up with a baby Trader Llama and an adult Trader Llama (I only did the two).