Ubuntu Core Appliance No connection

Found this NCbox 11.0.3 - Can't connect Mysql - #6 by ebugnet

Last post suggested low SD memory and so I put RPi SD card into Laptop and Gparted tells me the writable partition is full (14.54 out of 14.56 GB used)

However, Disk Usage analyser tells me there is only 1.4 GB on the Writable partition

I then used sudo du -h | grep -P '^[0-9\.]+G' to find out that 13GB of this is in

./system-data/var/snap/nextcloud/common/nextcloud/data/Leigh/files_versions/Nextcloud

Under this were folders corresponding to some of my folders that were being uploading from my laptop to Nextcloud when I had the problem

So it looks to me that when I change a lot of files on my laptop (in this case Digikam changed a lot of my photos with face tags) the Nextcloud appliance then stores them temporarily on the actual SD in the RPi before transferring them to the RPi /Nexcloud box external disk?

So, if this is the case, how can I (a) free up the space on my RPi SD card, and (b) stop this from happening in the future?