Forwarding Multiple PDFs In Outlook -- But They All Open The Same

So I have an Outlook e-mail with two (or more) different PDFs attached.

So I block copy both PDFs.

So I open a new message, and Paste the multiple PDFs.

And sometimes my recipient clicks on both (differently-titled) PDF attachments, only to find that they open as the same (first) image.

This happens sometimes (less often) when I Forward the original message with attachments.

Why, and how to avoid?