https://userapps.support.sap.com/sap/support/knowledge/en/2686534
2686534 - WSOA6 deletes former site assignment | SAP Knowledge Base Article
When assigning a site to an assortment in WSOA6, which has already at least one site assigned, the new site assignment deletes the first existing assignment.
former sitesap knowledgeassignmentbasearticle