This issue can be caused by there being Multiple vehicles with the same Registration.
The bug which allowed multiple vehicles to be set up with the same registration numbers has been fixed and this is no longer possible to do.
There is a possibility that any duplicate vehicles have not been removed from the database.
To check if there is a vehicle with a duplicate Registration No
Go to the Roundsman \ Vehicles menu and select the Vehicles Details screen.
Click on the Registration No column header to sort the table.
Check for any Duplicates.
If you find any, check both entries data values and when you know which one shouldn't be there, Click Edit and rename the Registration field. (and an X or something to make it unique)
Test your report.
If the report is still not correct, please raise a case with the Support Team.