Yes, the location of Basic-Fit was wrong or outdated (the mapper who created it had put Av. Boulevard/Bolwerklaan 21).

POI found on https://www.mapillary.com/app/?pKey=1802733303563437 and relocated + added door.

This is a very common occurrence: some business show an address on their website and it turns out they made it up because that number is neither printed on the door nor in any official government database. As a temporary fix, we can use contact:street and contact:housenumber, which is supported by Nominatim (this is a little better than adding a non-existing address on its own).