dovecot - Sep 2016 - Shared mailboxes nightmare (for me :-( )

Hi everybody,

I am honestly desperate: I have spent/invested the whole day in trying to set a
shared mailbox, with quite partial success. The INBOX is merged with the top
level mailbox, and there are many more folders. To give an idea, for the shared
account sharedacc at domain.org, this is how looks the folder structure:

sharedacc
  |-folderA
  |-folderB
  \-folderC

in the account for usera at domain.org, I see the following:

usera
  |-folderD
  |-folderE
  |-folderF
  \-shared
     \-sharedacc

So, I do not get to see folderA, folderB, folderC, etc.

My configuration is:

    # 2.2.25 (7be1766): /etc/dovecot/dovecot.conf
    # Pigeonhole version 0.4.14 (099a97c)
    # OS: Linux 4.5.4-0 x86_64 Debian stretch/sid zfs

    mail_plugins = zlib expire acl

    plugin {
    acl = vfile
    acl_shared_dict = proxy::acl
    }

    dict {
    acl = mysql:/etc/dovecot/dovecot-dict-sql.conf.ext
    }

    namespace {
    list = children
    location =
mdbox:/mnt/vmail/%%d/%%n:INDEXPVT=/mnt/vmail/indexes/shared/%%d/%%n
    prefix = shared/%%n/
    separator = /
    subscriptions = yes
    type = shared
    }

    protocol lmtp {
    mail_plugins = zlib expire acl sieve
    }

    protocol imap {
    mail_plugins = zlib expire acl antispam imap_acl
    }

the files I have one the account for sharedacc are:
    sharedacc
      |-dovecot-acl
      |-dovecot-acl-list
      \-mailboxes
          |-dovecot-acl
          |-folderA
          |   \-dbox-Mails
          |       \-dovecot-acl
          |-folderB
          |   \-dbox-Mails
          |       \-dovecot-acl
          \-folderC
              \-dbox-Mails
                  \-dovecot-acl

In dovecot-acl-list I have the following contents:
    1474920778 folderA
    1474920778 folderB
    1474920778 folderC

and in every dovecot-acl, I have:
    user=usera at domain.org  akxeilprwts

All the files on the filesystem are owned by the same vmail user.
What is strange is that I can see all these folderA, folderB, folderC in
roundcube, and I can click to subscribe to them. However, when I go back to the
general view, the subscriptions have been reset and I see only sharedacc,
without a thing inside. Finally, in kmail I can see the subscribed folders
without a problem (??!)

Can please somebody help me?