When opening and closing a mail multiple times while it is still in the message preview and then selecting to change your changes to the mail attachments are sometimes saved as unencrypted attachments. This leads to the infamous message when opening it again.

Hight priority because that could cause a plaintext leak as the unencrypted attachment was then sometimes synced back to the server.

As the user was asked to "save the changes" and the changes were to decrypt the message it had some user interaction.