https://koha-community.org/manual/latest/en/html/circulation.html#claiming-an-item-as-returned The manual says: "The claimed returned item will stay in the patron’s checkouts, and its lost status will be updated." The claimed item may or may not stay in the patron's checkouts based on the settings in the MarkLostItemsAsReturned system preference. The item's lost status will not always be updated when claimed. Since Bug 27919, when an item already has a lost status prior to being claimed its lost status does not change when claimed. This is noted in the ClaimReturnedLostValue system preference: "This will not update the lost status of the item if there is already an existing lost status set."
Thanks Andrew!