Update #2 [Fri 31st Mar, 2023 08:35 BST]:
Serebii.net webmaster Joe Merrick has provided another update about this issue via social media:
"Getting reports of more people from outside of Japan who reported the save bug getting contacted for their saves to be restored. Glad this is getting fixed, even though it's super rare"
Update #1 [Sat 11th Mar, 2023 13:30 GMT]:
While there's an update on the way for Pokémon Scarlet and Violet that will address some bug issues tied to eggs, there's been no mention about a fix for the reported corrupted save file problems.
In a slight development, Serebii.net webmaster Joe Merrick has mentioned on social media how The Pokémon Company is aware of this latest report. So hopefully a patch is on the way. In the meantime, it's believed to be a "very, very rare" scenario, if you do encounter it.
"Right so obviously people are wondering about the save data glitch, and rightfully so. TPC are aware. That I can guarantee as last week I messaged them myself about it. It's very, VERY, rare We do not know the cause. It's not GO, or buying the DLC...I, and many others including friends who are far more skilled than I at this sort of thing, have been trying everything to replicate it to no avail. With us being unable to, I imagine Nintendo and GF would also be working to narrow it down."
Original story [Tue 7th Mar, 2023 02:05 GMT]:
It added a number of new features, made some adjustments, and also included a lengthy list of bug fixes. Unfortunately, it seems to have introduced a major glitch. As highlighted by Kotaku, Scarlet and Violet players are now losing their saves.
Since the release of Version 1.2.0, players have reportedly been losing/corrupting their entire save files when performing certain tasks like connecting to Pokémon GO or downloading the recently announced DLC.
A number of players have reached out to Nintendo support, with one trainer being told by a representative that the company was already "looking into it". Another rep suggested transferring the Pokémon on the corrupt save file to Pokémon HOME - when the new games are made compatible with the storage app.