dovecot - Jan 2018 - Duplicate mailbox id, mailbox does not exist when attempting to give a new guid

Hi,

We have one user whose mailbox cannot replicate as below, dovecot 
version is: 2.2.13

mail.log shows the below for the user:

Jan? 3 16:20:57 hostname dovecot: dsync-server(user): Error: Duplicate 
mailbox GUID <guid number> for mailboxes <mailbox name.sub folder>
and
<mailbox name.sub folder> - giving a new GUID <guid number> to
<mailbox
name.subfolder>

Jan? 3 16:20:57 hostname dovecot: dsync-server(user): Error: Couldn't 
update mailbox <sub folder name> GUID: Mailbox doesn't exist: <sub 
folder name>

Looking at their mailbox the folder does exist.

If you are able to assist that would be appreciated.

Kind regards

Daniel Botting

Codethink Ltd