Print Receivables Transactions not sending Zipped PDFs Output

Summary:

During the 'Print Recivables Transactions' Scheduled Process for a single transaction, we set the Output Format of the file to be Zipped PDFs before executing the process expecting a single email with all the PDF Invoices zipped and included as an attachment.

However, we instead received multiple emails with individual invoices (i.e. 6 unzipped pdf invoices and 6 separate emails). In the 'Reports & Analytics' section we already set Zipped PDF as one of the available output formats. Take note that this Transaction contains multiple installments.

Please advise as what could be the cause of the system not compiling all invoices into a single Zipped file and sending it to the customer in a single email.