I just encountered that if I search for a house-number having 3 (or more?) digits, nominatim does not return the correct result even though the house number is contained in the OSM data. Is this a known issue? I couldn’t find anything…
Examples (see list of results on the left; it should contain exactly one result in both cases, but second query returns several locations):
Hm… I tried several house numbers yesterday, but I’ve chosen the wrong numbers… 153, for example, is correctly found. Thus I played around a little bit longer: the problem seems to be somewhat specific for the street “Kriegsstraße”. In some parts of the streets it seems to be a matter of the street side (or lane): odd numbers are found, even numbers not.
Despite this fact I still think that the actual problem must be in the Nominatim/search algorithm… This is because if I provide a viewbox as “hint”, I can find any number.