Upon attempting to destroy a weaponsmith villager's job station to give it a new job, it would not search for a new job, even though I had not traded with that villager previously. However, other villagers would take the weaponsmith's job when the station was replaced. This resulted in about 4 weaponsmiths that I had not traded with previously along with 1 that I had traded with previously. These villagers are sitting and staring at a single weaponsmith job station, and I have stopped picking up and replacing these stations for the fear that I will create more. I have, however, destroyed and replaced other job stations and observed the expected result of: villager roams for a job and takes an open job station.
TO SUMMARIZE:
The weaponsmith will not search for a new job, regardless of whether previous trades had taken place, even if another villager has taken what was previously its job station or the station has been destroyed.
Please check if that's still an issue for you in the latest 1.14.4 stable release or the latest 1.15 development snapshot.