Apple Mail 2.3774.300.61.1.2 seems to have problems handling inline attachments in replies

Background: This seems like a new problem that has started in the last couple days.

How to reproduce:

1. I receive an email which contains inline images in the sender's email signature on my Apple Mail 2.3774.300.61.1.2.
2. I click reply on the email and make sure images are displayed
3. I attach a file like a PDF to the reply and click send
4. The person I sent to has a mangled email where the inline images show as attachments and look like they have been taken out of the body of the email