The dispute_reason table is being populated from invoice_header table.
The current PK for dispute_reason table is id (i.e dispute_reason id ). One dispute_reason_id can be linked to multiple invoice headers, but since here we just have one pk i.e dispute_reason_id , we are overriding it with different invoice_header ids.
Ideally we should be creating separate records for unique invoice_header_id and dispute_reason_id.
For this, we need to include invoice_header_id also as the PK for dispute_reason table.