Rat catcher, “wandering can not work”? What would the rat catcher need in order to work? There is a rat problem by the icons and warnings.
(A learning question because my game is screwed at this point. All labours are going to gather the bodies of the dead and getting trapped. Down to three labours and no immigration. Also buildings that had repair issues and fixed are falling a part again and no labours for repairs. This game just turn into bad nightmare and sucks. 
If you provide a screenshot it might help.
First off, how many people do you have?
I dont know if its general for everyone, but a rat catcher only makes sense when theres infestation of rats, and that seem to be a problem ONLY by some minimum number of people in your village. In my case, it all started when i achieved 400+. That was when i finally saw the “rat icon” over houses and storages. Never before that number the rat catcher really worked and i had this construction since i was by the year 20 or something.
Send a picture to help identifying your issues. 
There are icons on all the food buildings and population is around 200 and dropping fast. Labours are down to three. Lastly how will picture help. This about why the rat catchers can not do there job?
You will need to make sure you have enough rat catchers to remove all of the infestations. Additionally, you will also need to make sure that the infested structures fall within the range of the rat catcher. This can be done in the same way you can move the range of hunters, foragers, etc.
Also, the rats will return over and over but as long as the rat catchers’ rangers encompass the buildings with the rat icon over them they will eventually be removed.
I have noticed that structures that deal with foodstuffs will be susceptible to rat infestations. Storehouses, granaries, root cellars, residences and markets will be targeted. I am not sure if bakeries can get infested. At any rate, make sure they’re covered and the rats will be removed over time.