As mentionned on Twitter, when Nominatim returns more than one result for a location, it is common that the default value be an administrative boundary, which is usually located in very weird places (on the outside of the boundary).

It would be best to sort the Nominatim results, giving preference to "place" and "amenity" classes before others, so as to select a location that makes sense when people search for, e.g. a city name.

See for example a search on Chambery which returns this json, where the best point to pick would be ID 1522668290 (Chambéry, Savoie, Rhône-Alpes, 73000, France), which is a place.