I have no idea why this street is connected to a postal code in Bulgaria via Nominatim.
See 'search by name' at the bottom of https://nominatim.openstreetmap.org/ui/search.html?q=https%3A%2F%2Fwww.openstreetmap.org%2Fway%2F128515324

I've asked the Nominatim maintainer about it, maybe we'll hear something from them.