Basically in the new 1.3 snapshots there must be a new much shorter range for the locate command and because woodland mansions are so rare 99% of the time /locate wont find one and just returns "could not find that structure nearby" which is a problem because after about 20 new world attempts I have figured out that the "cartographer" village will only sell ocean monument and woodland explorer maps if they are within the same short range as the locate command has to be to the monument/mansion structure, and now the range is so small they will almost never be close enough and wont sell the maps anymore making them unfindable other than flying around in creative for hours. This was not an issue in 1.12.2 and I assume is a problem with the new world generation which will completely breaks the cartographer villager and /locate command.