Special procurement type &2 is used for material &1

What causes this issue?

Source of supply key &V3& has been entered in the material master
record. This key indicates that the special procurement type &V2& is
normally used.

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.