message/external-body issues

Message had an attachment, and I did `vm-save-all-attachments'. The button showed

  [PDF: external: full1.pdf, PDF ...]

Then I hit return on the external attachment in order to view it, and it became two buttons:

 [PDF: full1.pdf, PDF]
 [PDF: external: full1.pdf, PDF ...]

If I hit return once more then another copy of the first line is generated.

I went to the first line and hit return in order to view it, and that worked.

Then I saved this retrieved version of the attachment via the first button. Then it became

  [Deleted full1.pdf (PDF)]
  [PDF: external: full1.pdf, PDF ...]

Hitting further return on this button didn't help.

Hitting return on the second button created a yet another button, but with an error message:

  [Deleted full1.pdf (PDF)]
  [MIME part missing header/body separator line]
  [PDF: external: full1.pdf, PDF ...]

Looking at the text of the message body showed

  [Deleted full1.pdf]
  [Saved to ...]
  --=_FvASF1Lxr25PSVxNK4KTb6A--

The original text part of the message was gone. The Content-Type in the header of the message had application/pdf, whereas it should have been multipart/mixed.

Trying to refresh the message from the server gave an error message

  VM internal error: headers of a message have been corrupted. Continue? (y or n)

Doing vm-decode-message shows that the message was indeed corrupted.