We have come across this. If you have Guardian, you can download KBA NK-1200-0263 DeltaV Diagnostics May Not Display the Correct Serial Numbers for Some Logic Solvers and SISNet Repeater.
Pasting snippets here for your reference: :)

This Knowledge Base Article, NK-1200-0263, documents an issue where DeltaV Diagnostics may not display the correct
serial number for some Logic Solvers and SISNet Repeaters.
The serial numbers of the Logic Solver cards and SISNet repeaters are available in DeltaV Diagnostics. These values
should be unique. However, it was found that the location information of a certain batch of hardware could not be
decoded by the controller. As a result, different or duplicate serial numbers appear in the card’s serial number
diagnostic attribute.
Workaround:
To determine the correct serial number, refer to the label on the Logic Solver and/or SISNet repeater.
Performing an advanced telnet to the affected Logic Solver and/or SISNet repeater will also provide the correct serial
number information. For assistance in performing this procedure, please contact the Global Service Center.
Note The discrepancy in the serial number shown in Diagnostics does not have any impact on operations.
Resolution:
Please refer to KBA AP-0800-0154: DeltaV Safety Instrumented Systems (SIS) Software Updates. Follow the link to
Incident TFS106546 to download the latest hotfix.
This issue has been resolved in DeltaV v12.3