Assignment to customer hierarchy not possible; not unique

What causes this issue?

Customer &V1& cannot be assigned to customer &V2&.
The customer hierarchy already contains various hierarchy notes for
customer &V2&. These hierarchy nodes are assigned to various different
sales areas. At least two of the sales areas could be assigned to the
sales area currently being processed as superordinate sales area.

System Response

You cannot carry out the hierarchy assignment here, since no unique
assignment can be determined from the data in the system.

How to fix this error?

Create the customer master data without maintaining the hierarchy
assignment. Then maintain the customer hierarchy using transactions
VDH1 or VDH1N.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.