I own a vanilla server with a few friends, with only a few datapacks that wouldn't affect this issue. 

As wandering traders are annoying, I killed one. This then provoked its llamas to attack me. I then tried to tame it, and successfully did. The llama then continued to attack me, while I was on it, continuously turning in a circle like a dog chasing its tail. I'm pretty sure this isn't intended.

I tried to recreate this with just summoning a trading llama, but that didn't work as it ran away instead of attacking it, meaning you have to kill a trader to do it.