dovecot.index.log: duplicate transaction log sequence (3)

[mabi]

Hello,

I am running Dovecot 2.3.5.1 on OpenBSD 6.5 with RainLoop as IMAP webmail client and just noticed the following error messages about duplicate transaction log sequences in the index log:

Jul 01 13:15:58 Error: imap(<REMOVED_EMAIL1>)<21324><TVSmwJyMd0C5D+Vb>: Transaction log /var/vmail/<REMOVED_DOMAIN>/<REMOVED_EMAIL1>/dovecot.index.log: duplicate transaction log sequence (3)
Jul 02 16:33:35 Error: imap(<REMOVED_EMAIL2>)<6812><gn4yobOMJlW5D+Vb>: Transaction log /var/vmail/<REMOVED_DOMAIN>/<REMOVED_EMAIL2>/dovecot.list.index.log: duplicate transaction log sequence (2)
Jul 02 16:33:35 Panic: imap(<REMOVED_EMAIL2>)<6812><gn4yobOMJlW5D+Vb>: file mail-index-write.c: line 137 (mail_index_write): assertion failed: (file->hdr.prev_file_seq == hdr->log_file_seq)
Jul 02 16:33:35 Fatal: imap(<REMOVED_EMAIL2>)<6812><gn4yobOMJlW5D+Vb>: master: service(imap): child 6812 killed with signal 6 (core not dumped - https://dovecot.org/bugreport.html#coredumps - set service imap { drop_priv_before_exec=yes })

Could this problem occur because I am using a Linux NFS server to store all the mails mounted under /var/mail ?

Any hints what I can do to avoid these error messages?

Thank you in advance.

Best regards,
Mabi