Diagnosis
The standard indicator of the payment card details has not beenmaintained for only one entry.

Procedure
The standard indicator must be set for only one set of payment carddetails.
When new payment card details are created, the first new payment carddetails must be given the standard indicator.
If a business partner has several payment card details and you want todelete payment card details with the standard indicator, you mustassign the standard indicator to other payment card details before thisdeletion takes place.