Fog when the metar reports CAVOK

Even if METAR has priority over Meteoblue values, maybe you can check MB forecast Weather Maps | Live Satellite & Weather Radar - meteoblue to determine if visibility is coming from that source or not.
Also check what is saying the ATIS at your destination airport, from what I understand, ATIS information is coming from MB and not METAR ATIS not Matching METAR