I tried speaking to a wandering trader, but noticed first that a llama had gotten stuck in a pond. After freeing the llama by breaking some dirt blocks, I checked what his available trades were, and closed the trade window to get emeralds from my base to pay, but as soon as the prompt closed, the wandering trader started moving around very quickly and very erratically, around the same speed one might move if they had used the maximum effect of speed potion and started sprinting around as if wildly moving their mouse around on a horizontal axis. I haven't been able to click on him to see if I can get him to stop.

Quick update: Just clicked on him, he only stopped while the prompt was open. The trade was completed, and resumed sprinting around the moment the window closed again.