Some PDF attachments are not coming through after a submission

I have a form that auto populates 48 different documents from one form (it creates a load of policies hence the need for 48 separate documents). In the settings tab I have "select all" selected to make sure they are all attached to the email after submission. However we have used this approximately 20 times since building the form and each time a different PDF is missing. 

This happens even though we have all the documents ticked.

Can you please sort this out?

May we know the attached PDF document that is missing in the notification email?

Or the PDF document being attached in the notification email is inconsistent?

If possible, can you split the PDF document attached into two notification email and let us know if the issue still remains?

So each time I do it a different PDF document is missing. No pattern or consistency, and sometimes it works fine. 

May we know if the form is embedded to a web page?

I have tested a sample form and I am able to view all the attached PDF.

May we know your email provider?

I have cleared also your form cache.

Let us know if the issue still remains.