Problem: Mails with attachment are duplicated hundreds of times in Sent folder

[Timo Schmiade]

Hi all,

I have a very strange issue with offlineimap. My MUA is mutt and it is
configured to store sent mail in my 'Sent' folder. Now, when a sent mail
is stored there and it has an attachment, the mail sometimes seems to
get copied over and over inside the 'Sent' folder, multiplying hundreds
of times over the course of days.

These copies are then sync'ed with the IMAP server, which has them show
up on all machines I sync my mails on. Interestingly, it happens only
and exclusively with the 'Sent' folder.

OS: Arch Linux 64 bit

# offlineimap --info
OfflineIMAP 6.5.5
  Licensed under the GNU GPL v2+ (v2 or any later version)

I tried reproducing the bug forcefully while capturing debugging output
but failed. So my question is:

Is this a known bug?

Kind regards,

Timo