Wandering traders do not despawn unless player leaves area

Put the summary of the bug you're having here

What I expected to happen was...:
Wandering traders would despawn, and only one wandering trader would exist at one time

What actually happened was...:
Three wandering traders naturally spawned, a few in-game days apart.

Steps to Reproduce:
1. Wait until wandering trader spawns.
2. Wait more time until another spawns, and observe that two wandering traders exist.