Raw Backtrace Error when backing up specific user

[Marius Fassbender]

Hi,

probably since the update to 2.3.1 I can't backup a specific users mailbox.

For backup I use the command 'dsync -o plugin/quota= -f -u user at domain 
backup dbox:/backup/dir'
When I execute this command with the -D option, I get to see

(above only Debug messages)
dsync(user at domain): Panic: file mailbox-attribute.c: line 362 
(mailbox_attribute_get_stream): assertion failed: (value_r->value != 
NULL || value_r->value_stream != NULL)
dsync(user at domain): Error: Raw backtrace: 
/usr/lib64/dovecot/libdovecot.so.0(+0xcc724) [0x7f0f15364724] -> 
/usr/lib64/dovecot/libdovecot.so.0(default_fatal_handler+0x2a) 
[0x7f0f1536476a] -> /usr/lib64/dovecot/libdovecot.so.0(i_fatal+0) 
[0x7f0f152d524b] -> /usr/lib64/dovecot/libdovecot-storage.so.0(+0x566ac) 
[0x7f0f156686ac] -> doveadm(dsync_mailbox_import_attribute+0x4d) 
[0x5581a663bf4d] -> doveadm(dsync_brain_sync_mails+0x2ef) 
[0x5581a66377ff] -> doveadm(dsync_brain_run+0x2b0) [0x5581a6632e90] -> 
doveadm(+0x2960c) [0x5581a661a60c] -> doveadm(+0x2b4f7) [0x5581a661c4f7] 
-> doveadm(+0x2c0dc) [0x5581a661d0dc] -> 
doveadm(doveadm_mail_try_run+0x205) [0x5581a661da75] -> 
doveadm(main+0x475) [0x5581a660cce5] -> 
/lib64/libc.so.6(__libc_start_main+0xf5) [0x7f0f14ca3c05] -> 
doveadm(+0x1be65) [0x5581a660ce65]
cancelled

my dovecot -n output:
# 2.3.1 (0580a21bf): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.5.1 (d9bc6dfe)
# OS: Linux 3.10.0-693.21.1.el7.x86_64 x86_64 CentOS Linux release 
7.4.1708 (Core)  xfs
doveconf: Warning: please set ssl_dh=</etc/dovecot/dh.pem
doveconf: Warning: You can generate it with: dd 
if=/var/lib/dovecot/ssl-parameters.dat bs=1 skip=88 | openssl dhparam 
-inform der > /etc/dovecot/dh.pem
auth_cache_negative_ttl = 0
auth_cache_size = 100 M
auth_master_user_separator = *
auth_mechanisms = login plain
auth_verbose = yes
auth_verbose_passwords = sha1:16
deliver_log_format = msgid=%m from=%f subject=%s psize=%p status=%$
first_valid_gid = 5000
first_valid_uid = 5000
hostname =
imap_capability = +XLIST
imap_client_workarounds = tb-extra-mailbox-sep tb-lsub-flags
last_valid_gid = 5000
last_valid_uid = 5000
lmtp_rcpt_check_quota = yes
lmtp_save_to_detail_mailbox = yes
mail_attachment_dir = /storage/mail/attachments
mail_attachment_hash = %{sha512}
mail_gid = 5000
mail_home = /storage/mail/settings/%Ld/%Ln
mail_location = sdbox:/storage/mail/mails/%Ld/%Ln
mail_plugins = zlib quota acl listescape fts fts_lucene
mail_server_admin = mailto:postmaster at domain
mail_uid = 5000
managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope 
encoded-character vacation subaddress comparator-i;ascii-numeric 
relational regex imap4flags copy include variables body enotify 
environment mailbox date index ihave duplicate mime foreverypart 
extracttext imapsieve vnd.dovecot.imapsieve
namespace {
   list = children
   location = sdbox:/storage/mail/mails/%%d/%%n
   prefix = shared/%%u/
   separator = /
   subscriptions = no
   type = shared
}
namespace inbox {
   inbox = yes
   location =
   mailbox Archive {
     special_use = \Archive
   }
   mailbox Archives {
     special_use = \Archive
   }
   mailbox Drafts {
     auto = subscribe
     special_use = \Drafts
   }
   mailbox "Gesendete Objekte" {
     special_use = \Sent
   }
   mailbox Junk {
     special_use = \Junk
   }
   mailbox Sent {
     auto = subscribe
     special_use = \Sent
   }
   mailbox "Sent Messages" {
     special_use = \Sent
   }
   mailbox Trash {
     auto = subscribe
     special_use = \Trash
   }
   prefix =
   separator = /
   subscriptions = yes
   type = private
}
passdb {
   args = /etc/dovecot/passwd.masterusers
   driver = passwd-file
   master = yes
   pass = yes
}
passdb {
   args = /etc/dovecot/dovecot-ldap.conf.ext
   driver = ldap
}
plugin {
   acl = vfile:/storage/mail/settings/global-acls:cache_secs=300
   acl_shared_dict = file:/storage/mail/settings/shared-mailboxes
   fts = lucene
   fts_autoindex = yes
   fts_lucene = whitespace_chars=@.
   imapsieve_mailbox1_before = 
file:/usr/lib64/dovecot/sieve/report-spam.sieve
   imapsieve_mailbox1_causes = COPY
   imapsieve_mailbox1_name = Spam
   imapsieve_mailbox2_before = 
file:/usr/lib64/dovecot/sieve/report-ham.sieve
   imapsieve_mailbox2_causes = COPY
   imapsieve_mailbox2_from = Spam
   imapsieve_mailbox2_name = *
   mail_log_fields = uid box msgid size subject
   quota = dict:User quota::file:%h/dovecot-quota
   quota_grace = 5%%
   quota_rule = Trash:storage=+5%%
   quota_warning = storage=95%% quota-warning 95 %u
   quota_warning2 = storage=80%% quota-warning 80 %u
   sieve = file:%h/sieve;active=%h/.dovecot.sieve
   sieve_execute_bin_dir = /usr/lib64/dovecot/sieve
   sieve_global_extensions = +vnd.dovecot.pipe +vnd.dovecot.execute
   sieve_pipe_bin_dir = /usr/lib64/dovecot/sieve
   sieve_plugins = sieve_imapsieve sieve_extprograms
   zlib_save = gz
   zlib_save_level = 6
}
postmaster_address = postmaster at domain
protocols = imap lmtp sieve
service auth {
   unix_listener /var/spool/postfix/private/auth {
     group = postfix
     mode = 0600
     user = postfix
   }
   unix_listener auth-userdb {
     group = dovemail
     mode = 0600
     user = dovemail
   }
}
service lmtp {
   inet_listener lmtp {
     address = 127.0.0.1
     port = 24
   }
   unix_listener /var/spool/postfix/private/dovecot-lmtp {
     group = postfix
     mode = 0600
     user = postfix
   }
}
service managesieve-login {
   inet_listener sieve {
     port = 4190
   }
}
service quota-warning {
   executable = script /usr/local/bin/quota-warning.sh
   unix_listener quota-warning {
     user = dovemail
   }
   user = dovecot
}
ssl = required
ssl_cert = </etc/pki/tls/certs/cert.cer
ssl_dh =  # hidden, use -P to show it
ssl_key =  # hidden, use -P to show it
userdb {
   args = /etc/dovecot/dovecot-ldap.conf.ext
   default_fields = master_user=%u
   driver = ldap
}
protocol lmtp {
   mail_plugins = zlib quota acl listescape fts fts_lucene sieve
   postmaster_address = postmaster at domain
}
protocol imap {
   mail_plugins = zlib quota acl listescape fts fts_lucene imap_acl 
imap_quota imap_sieve imap_zlib
}


I tried to rebuild the settings files of this mailbox by deleting them 
and restart the service but this didnt help. A reboot did neither.

I dont know where to start fixing this problem, does anyone has an advice?

Thanks in advance