eDocument is active for source type &1, do not activate for &2

What causes this issue?

To avoid redundancy in the creation of eDocuments, it is recommended
that you activate only one source type for inbound or outbound processes
in SD.
Examples:
For outbound documents define that the eDocument is created either out
of outbound delivery or out of the goods issue.
For inbound documents define that the eDocument is created either out of
inbound delivery or out of the goods receipt.

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?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.