The Cs .rin table option (From the 1.1.2 V1 update.) to patch the process for this still works, there's a option to patch the file as well but since the patch likely changed things around I would avoid that as to not risk breaking the exe though it does create a backup for ease of restoring said patch.
Apply from the main menu then load into the game.
Nice amount of bug fixes for 1.2.0 in general, still can't leave from the river raid but at least some conditions for that issue were resolved and the new easter event should begin tomorrow. (More tokens and mini games probably.
)
More cats are spawned too now for whatever reason but it's part of the changelog so I suppose it matches how frequently the engine likes to spawn dogs around after this change, more pets than people in the game world if that keeps up.
EDIT: Anyways there's at least one still working alternative for keeping items, Budabum will perhaps update it for 1.2.0 fully but otherwise it seems everything still works so it's just the new items ID's getting found out from the added content also in this update.
EDIT: Already updated it seems.
[Link]
(Or here for the table itself.
[Link] Might need an account to download from the website.)