Other relationships exist; no change allowed

What causes this issue?

The business event has additional relationships that were not created
in this transaction. You are not allowed to change the business event
right now.

How to fix this error?

Delete all the relationships of the business event except those that
have been created in this transaction. They are:
A020 is a specialization of
A011 cost center assignment
A036 is organized by
A024 takes place in
After you have made the required changes, create the other
relationships again if required.

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.