Installing Nextcloud (contacts/calendar)…
Nextcloud is in maintenance mode - no apps have been loaded
Nextcloud is in maintenance mode
Maybe an upgrade is already in process. Please check the logfile (data/nextcloud.log). If you want to re-run the upgrade procedure, remove the “maintenance mode” from config.php and call this script again.
The installer for mailinabox stops at this point so not sure how to proceed?
Any help would be appreciated it-has anyone seen this before?
Thanks
For my understanding the “crucial part” of the update, i.e. the roundcube security update has been installed.
Did you try to disable the maintenance mode from nextcloud and rerun the update? The config file for nextcloud can be found in /usr/local/lib/owncloud/config/config.php and there you should be able to disable it. Remember to do a backup first 
Went in and removed the ‘maintenance’ => true, line from /home/user-data/owncloud.
Upgrade was able to complete through all the following modules.
Thanks