World Geocoding Service returns no candidates when using the findAddressCandidates for zipcode NG15 7AA with the parameter Location pointing to a certain region in southern central UK and a distance of 50,000.
Moving the XY to a different location seems to work, also changing the distance or searching for a different zip code, but the combination of this region, the 50,000 distance, and the specific zip code consistently do not work.