S4 HANA Upgrade 1709 -> 1909

During the S4 upgrade to R1909 I am dealing with a number incidents, related to the customizing of the Central Business Partner.

The Business Partner does not seem to be enforced in 1709, while it does in 1909.

At this moment the Central Business Partner is not (fully) customized, but you are able to create a Business Partner with Role Organization with transaction BP.

After the upgrade to 1909 I am unable to create any Business Partner with transaction BP.

Right after clicking on [Organization] in transaction BP, I get an error message ["It is not possible to create organizational units"] and are not able to create a Business Partner.

The CVI_UPGRADE_CHECK_RESOLVE report was run and led to the conclusion that more was needed than indicated by the report.

Hence, I probably need to implement the Central Business Partner according to the enclosed SAP building block configuration guides (Best Practices BN4 and J6).

Is there someone who encountered the same Problem?

It is not possible to create organizational units [Message no. R1422].

In what possible way(s), this Problem can be fixed?