Email forward with Attachment missing in iPhone Mail

When I use Mail to forward an email with a pdf attachment, the receiver complaint that there's no attachment in that email.

I feel surprise as I have already chosen with attachment.

When I try doing the forward email again, in the draft, I find that the attachment is really missing.

However, something strange is that when I scroll down the original email, I saw a forward icon next to the attachment. I click that forward icon and I can successfully forward that email with attachment.

I can't always scroll down to search for attachment to do forward.

What is the best method to do email forward with attachment?

Ivan