If you forward an encrypted Email the attachments are no longer displayed in the original email.
To recreate :
Press Forward => you see the new mail with the original message and the attachments
Press Cancel => Back to the original with no more attachments
Press Forward => you see the new mail with the original WITHOUT any the attachments.
Deselect email and select again (email gets decrypted again) attachments are back.
If you open the original email in a window of its own you 'll see that the attachments fanish from it during the open-/ceating of the forwarded message.