In trying to add a Subsidiary to a Customer record, the User is getting the following error: the system cannot process changes of the entity-subsidiary relationships entities with multiple subsidiaries can be shared between only vendor and customer records.
This is because the Customer Record is a polymorphic entity with an Other Relationship of Partner.
Go to Customer Record > click the Relationships tab.
Under Other Relationships > click into Partner.
On the Partner record > Click Edit.
Use the Actions drop down menu > Click Delete.