More than one JIT call was found for external call number &1

What causes this issue?

The system tried to find one call position for the external call number
&V1&. This was not possible because there are multiple call items for
this external call number and material.

System Response

It is not possible to determine the internal call number.

How to fix this error?

Instead of entering the external call number, enter the internal call
number and the call item directly.

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.