Supplier Site Creation Error: Definition PartySiteId of type Attribute is not found

Summary:

There is an error with the REST web service after trying to create new sites for existing suppliers.

Content (required):

Hello,

There is an error with the REST web service for creating supplier sites after trying to create new sites for existing suppliers. This error only comes out while trying to create sites for suppliers that were created manually through the UI, for those that were created through a web service there is no problem at all.

Is there something we have to change to be able to create new sites for suppliers that were created manually?

Resource: /fscmRestApi/resources/11.13.18.05/suppliers/{supplierId}/child/sites