Turning on Chronology in Stock is not an option for the client.
I guess the problem is customer using Rebuild stock maintenance, even though we warned them of unpredictable consequences.
Rebuild Stock maintenance has been changed somewhere a year ago an used to get a different stock results after running. If I remember it right in November 2021 it has been fixed and rebuilding stock does not result in a different stock. This has been confirmed by another our client.
The client ran the Rebuild stock maintenance in the last year or so and it resulted in such consequences.