Pay On Receipt AutoInvoice and ERS Import duplicate line number

Hello, I want ask about Pay On Receipt AutoInvoice

I run Pay On Receipt AutoInvoice with 100 invoice, and each 1 invoice have multiple lines, and I'm sure data invoice num is not same with other. 

After I run Pay On Receipt AutoInvoice and ERS Import then the result of ERS Import is some data rejected, and the log says : duplicate line number

I'm sure the data is not duplicate, and then I check for example 1 invoice can created to 3 invoice ID with same invoice number, and each new invoice have lines.

which should the only 1 invoice and multiple lines.

I think that invoice broke to 3 because the unit price is different (maybe group by unit price), but i''m not sure about this.