dovecot - Sep 2017 - problem with shared folders and acls - only able to share INBOX

Hi everybody, 

I have a problem that I cannot share subfolders of the mailboxes INBOX ,
e.g.  /Sent / Trash etc. but also no self created folders. 
The ACLs seem to be set right. 
I have the suspicion that the dictionary (
/var/lib/dovecot/db/shared-mailboxes.db ) is not updated - there are no
entries for the sub folders

I just cannot find the problem within my configuration. Many thanks for
having a look at it.

Cheers from Hamburg, Germany,
Christian 

Configuration attached: 
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# 2.2.27 (c0f36b0): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.4.16 (fed8554)
# OS: Linux 4.9.0-3-amd64 x86_64 Debian 9.1 
auth_debug = yes
auth_mechanisms = plain login
auth_verbose = yes
mail_debug = yes
mail_gid = vmail
mail_home = /var/vmail/mailboxes/%d/%n
mail_location = maildir:~/mail:LAYOUT=fs
mail_plugins = acl
mail_privileged_group = vmail
mail_uid = vmail
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

namespace {
  hidden = no
  ignore_on_failure = no
  inbox = no
  list = yes
  location
maildir:%%h/mail:INDEX=%h/shared/%%u:CONTROL=%h/shared/%%u:INDEXPVT=%h/share
d/%%u
  prefix = shared/%%u/
  separator = /
  subscriptions = yes
  type = shared
}

namespace inbox {
  inbox = yes
  location = 
  mailbox Drafts {
    auto = subscribe
    special_use = \Drafts
  }
  mailbox Sent {
    auto = subscribe
    special_use = \Sent
  }
  mailbox Spam {
    auto = subscribe
    special_use = \Junk
  }
  mailbox Trash {
    auto = subscribe
    special_use = \Trash
  }
  prefix = 
  separator = /
  subscriptions = yes
  type = private
}
passdb {
  args = /etc/dovecot/dovecot-sql.conf
  driver = sql
}
plugin {
  acl = vfile
  acl_shared_dict = file:/var/lib/dovecot/db/shared-mailboxes.db
  antispam_backend = pipe
  antispam_mail_notspam = learn_ham
  antispam_mail_sendmail = /usr/bin/rspamc
  antispam_mail_spam = learn_spam
  antispam_spam = Spam
  antispam_trash = Trash
  quota = maildir:User quota
  quota_exceeded_message = Benutzer %u hat das Speichervolumen
?berschritten. / User %u has exhausted allowed storage space.
  sieve
file:/var/vmail/sieve/%d/%n/scripts;active=/var/vmail/sieve/%d/%n/active-scr
ipt.sieve
  sieve_before = /var/vmail/sieve/global/spam-global.sieve
}
protocols = imap lmtp sieve
service auth {
  unix_listener /var/spool/postfix/private/auth {
    group = postfix
    mode = 0660
    user = postfix
  }
  unix_listener auth-userdb {
    group = vmail
    mode = 0660
    user = vmail
  }
}
service imap-login {
  inet_listener imap {
    port = 143
  }
}
service lmtp {
  unix_listener /var/spool/postfix/private/dovecot-lmtp {
    group = postfix
    mode = 0660
    user = postfix
  }
  user = vmail
}
service managesieve-login {
  inet_listener sieve {
    port = 4190
  }
}
ssl = required
ssl_cert = </etc/letsencrypt/live/mail.mydomain.org/fullchain.pem
ssl_cipher_list
EDH+CAMELLIA:EDH+aRSA:EECDH+aRSA+AESGCM:EECDH+aRSA+SHA256:EECDH:+CAMELLIA128
:+AES128:+SSLv3:!aNULL:!eNULL:!LOW:!3DES:!MD5:!EXP:!PSK:!DSS:!RC4:!SEED:!IDE
A:!ECDSA:kEDH:CAMELLIA128-SHA:AES128-SHA
ssl_dh_parameters_length = 2048
ssl_key =  # hidden, use -P to show it
ssl_prefer_server_ciphers = yes
userdb {
  args = /etc/dovecot/dovecot-sql.conf
  driver = sql
}
protocol imap {
  imap_idle_notify_interval = 29 mins
  mail_max_userip_connections = 20
  mail_plugins = acl quota imap_quota antispam imap_acl
}
protocol lmtp {
  mail_plugins = acl sieve
  postmaster_address = postmaster at mydomain.org
}
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