[Dovecot] Broken dovecot-uidlist files

[Ulrich Zehl]

I have just upgraded to 1.1.8, hoping to fix these types of errors:

Jan 20 10:39:27 laura deliver(xxxxxx at example.net): Broken file /srv/storage/mail/store/net/example/xx/xxxxxx/Maildir/dovecot-uidlist line 156: Invalid data:
Jan 20 10:41:19 laura dovecot: POP3(yy.yy at example.at): Broken file /srv/storage/mail/store/at/example/yy.yy/Maildir/dovecot-uidlist line 2: Invalid data:

Unfortunately, they still pop up. Since I suspect these errors to be
responsible for customers complaining about downloading mails twice, I'd
like to fix them.

Our setup has multiple servers sharing the same NFS-mounted directory for
maildirs and indexes; we have set
  mmap_disable = yes
  dotlock_use_excl = yes
  fsync_disable = no
  mail_nfs_index = yes
  lock_method = fcntl

As far as I can tell, for at least one of these errors, there was no
concurrent access to the mailbox in question.

What can I do to solve this problem, or to analyze it further?

Ulrich