I had the same issue with my wife yesterday. She was flying the return leg of a flight from MEL-NTL. On the way up, travelling solo, her BP showed her [partner] Gold status, on the way back it still showed her earlier Red Status although as she was travelling with me (Plat) it made no practical difference. I assume the system involved some kind of manual override on the way up when she checked in using her gold card but on the way back i handled the check in.