As far as I have observed, the wandering trader never targets a position and pathfinds toward it. The only way it changes its position is when its llamas push it. This happens every few seconds because the llamas almost constantly move, and they don't pull the trader when they get to the end of their leads, but they do push it every time they return.

The llamas can't push the trader up when they return from below it, but they'll always push it down when they return from above. The net effect is that the trader can only stay at the same level or move downward. Over time, the only possible outcomes are that it gets stuck in a corner, or it gets pushed into a concave depression/over the edge of a cliff/into a cave or ravine/into a pool, river, or ocean. In many of the latter cases, there's a good chance that it will die, and even if it doesn't, trading with it becomes less convenient. It's also absurdly suicidal behavior for the trader to allow its llamas to push it to such a fate.

Steps to reproduce:

1. Wait near a village (or at least a bed) until a wandering trader spawns.
2. Observe how its llamas push it every time they return from the end of their lead.
3. Observe that (unless the terrain is completely level) after enough time passes it always either gets stuck in a corner or falls into a depression, a cave, or water.