Bad sigpatches or a faulty NSP download. Fix: Download the NSP from a different source (verify CRC32 checksums if available). Update your hekate_ipl.ini and sigpatches to the latest version matching your firmware (e.g., FW 18.1.0).
While there isn't a single "official" blog post with that exact name, the most useful summaries for the latest Mario Kart 8 Deluxe Mario Kart 8 Deluxe Update -NSP-
Mario Kart 8 Deluxe is a geriatric racer. Mario Kart 8 Deluxe is the definitive version it's worth every penny. Metacritic Bad sigpatches or a faulty NSP download