Partner article number &1 double: matl no. &2 and matl no. &3

What causes this issue?

A duplicate entry has occurred. This is a grave error. Presumably, the
number range for the partner article numbers has been modified or reset
or incorrectly initialized without taking account of previous entries.
The error cannot occur if when the number ranges are set up correctly.

System Response

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

How to fix this error?

Error message extract from SAP system. Copyright SAP SE.