Mailbox suddenly inaccessible

[Sven Strickroth]

Hi,

out of the sudden I've an inaccessible folder with Dovecot 2.2.27
(c0f36b0) from Debian Jessy backports.

$ doveadm mailbox list -u mail at example.com
INBOX/Erledigt
INBOX/Erledigt/Erledigt
INBOX/Versicherung gesendet
Sent
INBOX

However, it is not accessible any more, my IMAP client tells me:
"STATUS: Mailbox doesn't exist: INBOX/Erledigt"

Also:
$ doveadm search -u mail at example.com mailbox INBOX/Erledigt
doveadm(mail at example.com): Error: Couldn't get mailbox 'INBOX/Erledigt'
GUID: Mailbox doesn't exist: INBOX/Erledigt

Other mailboxes (especially INBOX/Erledigt/Erledigt) are accessible:
$ doveadm search -u mail at example.com mailbox INBOX/Erledigt/Erledigt
60af0f1964d68d574a480000f94cf17a 346
60af0f1964d68d574a480000f94cf17a 367
...

$ doveadm -f table mailbox status -u mail at example.com  "messages vsize"
"INBOX*"
mailbox                     messages vsize
INBOX/Erledigt2             15       25868676
INBOX/Erledigt/Erledigt     4344     6107238270
INBOX                       24       36081472

I'm using mdbox and see no errors in syslog from dovecot.

Any ideas on what's going on and how I can recover the mails in that folder?

-- 
Best regards,
 Sven Strickroth
 PGP key id F5A9D4C4 @ any key-server